diff --git a/lib/review/book/base.rb b/lib/review/book/base.rb
index 6cad53f64..d094d7517 100644
--- a/lib/review/book/base.rb
+++ b/lib/review/book/base.rb
@@ -10,6 +10,7 @@
 require 'review/configure'
 require 'review/catalog'
 require 'review/book/bib'
+require 'review/book/cache'
 
 module ReVIEW
   module Book
@@ -19,6 +20,7 @@ class Base
       attr_accessor :catalog
       attr_reader :basedir
       attr_accessor :bibpaper_index
+      attr_reader :cache
 
       def self.load(basedir = '.', config: nil)
         new(basedir, config: config)
@@ -39,6 +41,8 @@ def initialize(basedir = '.', config: nil)
 
         @warn_old_files = {} # XXX for checking CHAPS, PREDEF, POSTDEF
         @basedir_seen = {}
+
+        @cache = ReVIEW::Book::Cache.new
         update_rubyenv
       end
 
diff --git a/lib/review/book/cache.rb b/lib/review/book/cache.rb
new file mode 100644
index 000000000..27f5f8d78
--- /dev/null
+++ b/lib/review/book/cache.rb
@@ -0,0 +1,54 @@
+#
+# Copyright (c) 2014-2024 Minero Aoki, Kenshi Muto, Masayoshi Takahashi
+#
+# This program is free software.
+# You can distribute or modify this program under the terms of
+# the GNU LGPL, Lesser General Public License version 2.1.
+# For details of LGPL, see the file "COPYING".
+#
+module ReVIEW
+  module Book
+    class Cache
+      def initialize
+        @store = {}
+      end
+
+      def reset
+        @store.clear
+      end
+
+      # key should be Symbol, not String
+      def fetch(key, &block)
+        raise ArgumentError, 'Key should be Symbol' unless key.is_a?(Symbol)
+
+        if cached?(key)
+          read(key)
+        else
+          exec_block_and_save(key, &block)
+        end
+      end
+
+      def cached?(key)
+        @store.key?(key)
+      end
+
+      private
+
+      def read(key)
+        @store[key]
+      end
+
+      def write(key, value)
+        @store[key] = value
+      end
+
+      def exec_block_and_save(key)
+        result = yield(key)
+
+        write(key, result)
+
+        result
+      end
+    end
+  end
+end
diff --git a/lib/review/book/image_finder.rb b/lib/review/book/image_finder.rb
index ed72fc841..cd6d89820 100644
--- a/lib/review/book/image_finder.rb
+++ b/lib/review/book/image_finder.rb
@@ -26,7 +26,9 @@ def entry_object(path)
       end
 
       def dir_entries
-        Dir.glob(File.join(@basedir, '**{,/*/**}/*.*')).uniq.sort.map { |entry| entry.sub(%r{^\./}, '') }
+        @book.cache.fetch(:image_finder_dir_entries) do
+          Dir.glob(File.join(@basedir, '**{,/*/**}/*.*')).uniq.sort.map { |entry| entry.sub(%r{^\./}, '') }
+        end
       end
 
       def add_entry(path)
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 3d3fcd1c0..da68b8be8 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -35,6 +35,7 @@ def compile_inline(text)
 def compile_block(text)
   method_name = "compile_block_#{@builder.target_name}"
   method_name = 'compile_block_default' unless self.respond_to?(method_name, true)
+  @chapter.book.cache.reset
   self.__send__(method_name, text)
 end