diff --git a/changelog/fix_an_incorrect_autocorrect_for_style_redundant_exception.md b/changelog/fix_an_incorrect_autocorrect_for_style_redundant_exception.md
new file mode 100644
index 000000000000..f1611a55d191
--- /dev/null
+++ b/changelog/fix_an_incorrect_autocorrect_for_style_redundant_exception.md
@@ -0,0 +1 @@
+* [#12177](https://github.com/rubocop/rubocop/pull/12177): Fix an incorrect autocorrect for `Style/RedundantException`. ([@ydah][])
diff --git a/lib/rubocop/cop/style/redundant_exception.rb b/lib/rubocop/cop/style/redundant_exception.rb
index 03e09f6eaa08..ee557e732f13 100644
--- a/lib/rubocop/cop/style/redundant_exception.rb
+++ b/lib/rubocop/cop/style/redundant_exception.rb
@@ -5,17 +5,21 @@ module Cop
     module Style
       # Checks for RuntimeError as the argument of raise/fail.
       #
-      # It checks for code like this:
-      #
       # @example
-      #   # Bad
+      #   # bad
       #   raise RuntimeError, 'message'
-      #
-      #   # Bad
       #   raise RuntimeError.new('message')
       #
-      #   # Good
+      #   # good
       #   raise 'message'
+      #
+      #   # bad - message is not a string
+      #   raise RuntimeError, Object.new
+      #   raise RuntimeError.new(Object.new)
+      #
+      #   # good
+      #   raise Object.new.to_s
+      #
       class RedundantException < Base
         extend AutoCorrector
 
@@ -30,26 +34,42 @@ def on_send(node)
           fix_exploded(node) || fix_compact(node)
         end
 
+        private
+
         def fix_exploded(node)
           exploded?(node) do |command, message|
             add_offense(node, message: MSG_1) do |corrector|
-              if node.parenthesized?
-                corrector.replace(node, "#{command}(#{message.source})")
-              else
-                corrector.replace(node, "#{command} #{message.source}")
-              end
+              corrector.replace(node, replaced_exploded(node, command, message))
             end
           end
         end
 
+        def replaced_exploded(node, command, message)
+          arg = string_message?(message) ? message.source : "#{message.source}.to_s"
+          arg = node.parenthesized? ? "(#{arg})" : " #{arg}"
+          "#{command}#{arg}"
+        end
+
+        def string_message?(message)
+          message.str_type? || message.dstr_type? || message.xstr_type?
+        end
+
         def fix_compact(node)
           compact?(node) do |new_call, message|
             add_offense(node, message: MSG_2) do |corrector|
-              corrector.replace(new_call, message.source)
+              corrector.replace(new_call, replaced_compact(message))
             end
           end
         end
 
+        def replaced_compact(message)
+          if string_message?(message)
+            message.source
+          else
+            "#{message.source}.to_s"
+          end
+        end
+
         # @!method exploded?(node)
         def_node_matcher :exploded?, <<~PATTERN
           (send nil? ${:raise :fail} (const {nil? cbase} :RuntimeError) $_)
diff --git a/spec/rubocop/cop/style/redundant_exception_spec.rb b/spec/rubocop/cop/style/redundant_exception_spec.rb
index a02ad1249ccb..1e36452690ad 100644
--- a/spec/rubocop/cop/style/redundant_exception_spec.rb
+++ b/spec/rubocop/cop/style/redundant_exception_spec.rb
@@ -4,54 +4,54 @@
   shared_examples 'common behavior' do |keyword, runtime_error|
     it "reports an offense for a #{keyword} with #{runtime_error}" do
       expect_offense(<<~RUBY, keyword: keyword, runtime_error: runtime_error)
-        %{keyword} %{runtime_error}, msg
-        ^{keyword}^^{runtime_error}^^^^^ Redundant `RuntimeError` argument can be removed.
+        %{keyword} %{runtime_error}, "message"
+        ^{keyword}^^{runtime_error}^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
       RUBY
 
       expect_correction(<<~RUBY)
-        #{keyword} msg
+        #{keyword} "message"
       RUBY
     end
 
     it "reports an offense for a #{keyword} with #{runtime_error} and ()" do
       expect_offense(<<~RUBY, keyword: keyword, runtime_error: runtime_error)
-        %{keyword}(%{runtime_error}, msg)
-        ^{keyword}^^{runtime_error}^^^^^^ Redundant `RuntimeError` argument can be removed.
+        %{keyword}(%{runtime_error}, "message")
+        ^{keyword}^^{runtime_error}^^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
       RUBY
 
       expect_correction(<<~RUBY)
-        #{keyword}(msg)
+        #{keyword}("message")
       RUBY
     end
 
     it "reports an offense for a #{keyword} with #{runtime_error}.new" do
       expect_offense(<<~RUBY, keyword: keyword, runtime_error: runtime_error)
-        %{keyword} %{runtime_error}.new msg
-        ^{keyword}^^{runtime_error}^^^^^^^^ Redundant `RuntimeError.new` call can be replaced with just the message.
+        %{keyword} %{runtime_error}.new "message"
+        ^{keyword}^^{runtime_error}^^^^^^^^^^^^^^ Redundant `RuntimeError.new` call can be replaced with just the message.
       RUBY
 
       expect_correction(<<~RUBY)
-        #{keyword} msg
+        #{keyword} "message"
       RUBY
     end
 
     it "reports an offense for a #{keyword} with #{runtime_error}.new" do
       expect_offense(<<~RUBY, keyword: keyword, runtime_error: runtime_error)
-        %{keyword} %{runtime_error}.new(msg)
-        ^{keyword}^^{runtime_error}^^^^^^^^^ Redundant `RuntimeError.new` call can be replaced with just the message.
+        %{keyword} %{runtime_error}.new("message")
+        ^{keyword}^^{runtime_error}^^^^^^^^^^^^^^^ Redundant `RuntimeError.new` call can be replaced with just the message.
       RUBY
 
       expect_correction(<<~RUBY)
-        #{keyword} msg
+        #{keyword} "message"
       RUBY
     end
 
     it "accepts a #{keyword} with #{runtime_error} if it does not have 2 args" do
-      expect_no_offenses("#{keyword} #{runtime_error}, msg, caller")
+      expect_no_offenses("#{keyword} #{runtime_error}, 'message', caller")
     end
 
     it 'accepts rescue w/ non redundant error' do
-      expect_no_offenses "#{keyword} OtherError, msg"
+      expect_no_offenses "#{keyword} OtherError, 'message'"
     end
   end
 
@@ -59,4 +59,70 @@
   include_examples 'common behavior', 'raise', '::RuntimeError'
   include_examples 'common behavior', 'fail', 'RuntimeError'
   include_examples 'common behavior', 'fail', '::RuntimeError'
+
+  it 'registers an offense for raise with RuntimeError, "#{message}"' do
+    expect_offense(<<~'RUBY')
+      raise RuntimeError, "#{message}"
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
+    RUBY
+
+    expect_correction(<<~'RUBY')
+      raise "#{message}"
+    RUBY
+  end
+
+  it 'registers an offense for raise with RuntimeError, `command`' do
+    expect_offense(<<~RUBY)
+      raise RuntimeError, `command`
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      raise `command`
+    RUBY
+  end
+
+  it 'registers an offense for raise with RuntimeError, Object.new' do
+    expect_offense(<<~RUBY)
+      raise RuntimeError, Object.new
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      raise Object.new.to_s
+    RUBY
+  end
+
+  it 'registers an offense for raise with RuntimeError.new, Object.new and parans' do
+    expect_offense(<<~RUBY)
+      raise RuntimeError.new(Object.new)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError.new` call can be replaced with just the message.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      raise Object.new.to_s
+    RUBY
+  end
+
+  it 'registers an offense for raise with RuntimeError.new, Object.new no parens' do
+    expect_offense(<<~RUBY)
+      raise RuntimeError.new Object.new
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError.new` call can be replaced with just the message.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      raise Object.new.to_s
+    RUBY
+  end
+
+  it 'registers an offense for raise with RuntimeError, valiable' do
+    expect_offense(<<~RUBY)
+      raise RuntimeError, valiable
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Redundant `RuntimeError` argument can be removed.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      raise valiable.to_s
+    RUBY
+  end
 end