diff --git a/package.json b/package.json
index 331bb1c..d588362 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@samchon/openapi",
-  "version": "0.4.5",
+  "version": "0.4.6",
   "description": "OpenAPI definitions and converters for 'typia' and 'nestia'.",
   "main": "./lib/index.js",
   "module": "./lib/index.mjs",
diff --git a/src/OpenApiV3.ts b/src/OpenApiV3.ts
index 2082e4d..2f91e3d 100644
--- a/src/OpenApiV3.ts
+++ b/src/OpenApiV3.ts
@@ -182,11 +182,11 @@ export namespace OpenApiV3 {
   export namespace IJsonSchema {
     export interface IBoolean extends __ISignificant<"boolean"> {
       default?: boolean | null;
-      enum?: boolean[];
+      enum?: Array<boolean | null>;
     }
     export interface IInteger extends __ISignificant<"integer"> {
       /** @type int64 */ default?: number | null;
-      /** @type int64 */ enum?: number[];
+      /** @type int64 */ enum?: Array<number | null>;
       /** @type int64 */ minimum?: number;
       /** @type int64 */ maximum?: number;
       exclusiveMinimum?: boolean;
@@ -199,7 +199,7 @@ export namespace OpenApiV3 {
     }
     export interface INumber extends __ISignificant<"number"> {
       default?: number | null;
-      enum?: number[];
+      enum?: Array<number | null>;
       minimum?: number;
       maximum?: number;
       exclusiveMinimum?: boolean;
@@ -208,7 +208,7 @@ export namespace OpenApiV3 {
     }
     export interface IString extends __ISignificant<"string"> {
       default?: string | null;
-      enum?: string[];
+      enum?: Array<string | null>;
       format?:
         | "binary"
         | "byte"
diff --git a/src/OpenApiV3_1.ts b/src/OpenApiV3_1.ts
index 2113352..a374a71 100644
--- a/src/OpenApiV3_1.ts
+++ b/src/OpenApiV3_1.ts
@@ -217,11 +217,11 @@ export namespace OpenApiV3_1 {
     }
     export interface IBoolean extends __ISignificant<"boolean"> {
       default?: boolean | null;
-      enum?: boolean[];
+      enum?: Array<boolean | null>;
     }
     export interface IInteger extends __ISignificant<"integer"> {
       /** @type int64 */ default?: number | null;
-      /** @type int64 */ enum?: number[];
+      /** @type int64 */ enum?: Array<number | null>;
       /** @type int64 */ minimum?: number;
       /** @type int64 */ maximum?: number;
       /** @type int64 */ exclusiveMinimum?: number | boolean;
@@ -234,7 +234,7 @@ export namespace OpenApiV3_1 {
     }
     export interface INumber extends __ISignificant<"number"> {
       default?: number | null;
-      enum?: number[];
+      enum?: Array<number | null>;
       minimum?: number;
       maximum?: number;
       exclusiveMinimum?: number | boolean;
@@ -244,7 +244,7 @@ export namespace OpenApiV3_1 {
     export interface IString extends __ISignificant<"string"> {
       contentMediaType?: string;
       default?: string | null;
-      enum?: string[];
+      enum?: Array<string | null>;
       format?:
         | "binary"
         | "byte"
diff --git a/src/SwaggerV2.ts b/src/SwaggerV2.ts
index ea6b8c4..9b84e80 100644
--- a/src/SwaggerV2.ts
+++ b/src/SwaggerV2.ts
@@ -132,11 +132,11 @@ export namespace SwaggerV2 {
   export namespace IJsonSchema {
     export interface IBoolean extends __ISignificant<"boolean"> {
       default?: boolean | null;
-      enum?: boolean[];
+      enum?: Array<boolean | null>;
     }
     export interface IInteger extends __ISignificant<"integer"> {
       /** @type int64 */ default?: number | null;
-      /** @type int64 */ enum?: number[];
+      /** @type int64 */ enum?: Array<number | null>;
       /** @type int64 */ minimum?: number;
       /** @type int64 */ maximum?: number;
       exclusiveMinimum?: boolean;
@@ -149,7 +149,7 @@ export namespace SwaggerV2 {
     }
     export interface INumber extends __ISignificant<"number"> {
       default?: number | null;
-      enum?: number[];
+      enum?: Array<number | null>;
       minimum?: number;
       maximum?: number;
       exclusiveMinimum?: boolean;
@@ -158,7 +158,7 @@ export namespace SwaggerV2 {
     }
     export interface IString extends __ISignificant<"string"> {
       default?: string | null;
-      enum?: string[];
+      enum?: Array<string | null>;
       format?:
         | "binary"
         | "byte"
diff --git a/src/internal/OpenApiV3Converter.ts b/src/internal/OpenApiV3Converter.ts
index 119a912..ac791ce 100644
--- a/src/internal/OpenApiV3Converter.ts
+++ b/src/internal/OpenApiV3Converter.ts
@@ -268,6 +268,14 @@ export namespace OpenApiV3Converter {
           if ((schema as OpenApiV3.IJsonSchema.INumber).default === null)
             nullable.default = null;
         }
+        if (
+          Array.isArray((schema as OpenApiV3.IJsonSchema.INumber).enum) &&
+          (schema as OpenApiV3.IJsonSchema.INumber).enum?.length &&
+          (schema as OpenApiV3.IJsonSchema.INumber).enum?.some(
+            (e) => e === null,
+          )
+        )
+          nullable.value ||= true;
         // UNION TYPE CASE
         if (TypeChecker.isAnyOf(schema)) schema.anyOf.forEach(visit);
         else if (TypeChecker.isOneOf(schema)) schema.oneOf.forEach(visit);
@@ -280,8 +288,15 @@ export namespace OpenApiV3Converter {
           TypeChecker.isNumber(schema) ||
           TypeChecker.isString(schema)
         )
-          if (schema.enum?.length)
-            union.push(...schema.enum.map((value) => ({ const: value })));
+          if (
+            schema.enum?.length &&
+            schema.enum.filter((e) => e !== null).length
+          )
+            union.push(
+              ...schema.enum
+                .filter((v) => v !== null)
+                .map((value) => ({ const: value })),
+            );
           else
             union.push({
               ...schema,
diff --git a/src/internal/OpenApiV3_1Converter.ts b/src/internal/OpenApiV3_1Converter.ts
index ebc905c..c1cd971 100644
--- a/src/internal/OpenApiV3_1Converter.ts
+++ b/src/internal/OpenApiV3_1Converter.ts
@@ -297,6 +297,15 @@ export namespace OpenApiV3_1Converter {
           if ((schema as OpenApiV3_1.IJsonSchema.INumber).default === null)
             nullable.default = null;
         }
+        if (
+          Array.isArray((schema as OpenApiV3_1.IJsonSchema.INumber).enum) &&
+          (schema as OpenApiV3_1.IJsonSchema.INumber).enum?.length &&
+          (schema as OpenApiV3_1.IJsonSchema.INumber).enum?.some(
+            (e) => e === null,
+          )
+        )
+          nullable.value ||= true;
+
         // MIXED TYPE CASE
         if (TypeChecker.isMixed(schema)) {
           if (schema.const !== undefined)
@@ -345,9 +354,10 @@ export namespace OpenApiV3_1Converter {
               visit({
                 ...schema,
                 ...{
-                  enum: schema.enum?.length
-                    ? schema.enum.filter((x) => typeof x === type)
-                    : undefined,
+                  enum:
+                    schema.enum?.length && schema.enum.filter((e) => e !== null)
+                      ? schema.enum.filter((x) => typeof x === type)
+                      : undefined,
                 },
                 type: type as any,
               });
@@ -355,9 +365,15 @@ export namespace OpenApiV3_1Converter {
               visit({
                 ...schema,
                 ...{
-                  enum: schema.enum?.length
-                    ? schema.enum.filter((x) => Number.isInteger(x))
-                    : undefined,
+                  enum:
+                    schema.enum?.length && schema.enum.filter((e) => e !== null)
+                      ? schema.enum.filter(
+                          (x) =>
+                            x !== null &&
+                            typeof x === "number" &&
+                            Number.isInteger(x),
+                        )
+                      : undefined,
                 },
                 type: type as any,
               });
@@ -370,8 +386,11 @@ export namespace OpenApiV3_1Converter {
           union.push(convertAllOfSchema(components)(schema));
         // ATOMIC TYPE CASE (CONSIDER ENUM VALUES)
         else if (TypeChecker.isBoolean(schema))
-          if (schema.enum?.length)
-            for (const value of schema.enum)
+          if (
+            schema.enum?.length &&
+            schema.enum.filter((e) => e !== null).length
+          )
+            for (const value of schema.enum.filter((e) => e !== null))
               union.push({
                 const: value,
                 ...({
@@ -390,8 +409,8 @@ export namespace OpenApiV3_1Converter {
               },
             });
         else if (TypeChecker.isInteger(schema) || TypeChecker.isNumber(schema))
-          if (schema.enum?.length)
-            for (const value of schema.enum)
+          if (schema.enum?.length && schema.enum.filter((e) => e !== null))
+            for (const value of schema.enum.filter((e) => e !== null))
               union.push({
                 const: value,
                 ...({
@@ -431,8 +450,11 @@ export namespace OpenApiV3_1Converter {
                   }),
             });
         else if (TypeChecker.isString(schema))
-          if (schema.enum?.length)
-            for (const value of schema.enum)
+          if (
+            schema.enum?.length &&
+            schema.enum.filter((e) => e !== null).length
+          )
+            for (const value of schema.enum.filter((e) => e !== null))
               union.push({
                 const: value,
                 ...({
diff --git a/src/internal/SwaggerV2Converter.ts b/src/internal/SwaggerV2Converter.ts
index f1cd896..2e29887 100644
--- a/src/internal/SwaggerV2Converter.ts
+++ b/src/internal/SwaggerV2Converter.ts
@@ -276,6 +276,12 @@ export namespace SwaggerV2Converter {
         if ((schema as SwaggerV2.IJsonSchema.INumber).default === null)
           nullable.default = null;
       }
+      if (
+        Array.isArray((schema as SwaggerV2.IJsonSchema.INumber).enum) &&
+        (schema as SwaggerV2.IJsonSchema.INumber).enum?.length &&
+        (schema as SwaggerV2.IJsonSchema.INumber).enum?.some((e) => e === null)
+      )
+        nullable.value ||= true;
       // UNION TYPE CASE
       if (TypeChecker.isAnyOf(schema)) schema["x-anyOf"].forEach(visit);
       else if (TypeChecker.isOneOf(schema)) schema["x-oneOf"].forEach(visit);
@@ -286,8 +292,12 @@ export namespace SwaggerV2Converter {
         TypeChecker.isNumber(schema) ||
         TypeChecker.isString(schema)
       )
-        if (schema.enum?.length)
-          union.push(...schema.enum.map((value) => ({ const: value })));
+        if (schema.enum?.length && schema.enum.filter((e) => e !== null).length)
+          union.push(
+            ...schema.enum
+              .filter((v) => v !== null)
+              .map((value) => ({ const: value })),
+          );
         else
           union.push({
             ...schema,