diff --git a/src/Data/Word/Adler32.hs b/src/Data/Word/Adler32.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Word/Adler32.hs
@@ -0,0 +1,43 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+{-# LANGUAGE BlockArguments, LambdaCase #-}
+{-# LANGUAGE ExplicitForAll #-}
+{-# LANGUAGE RequiredTypeArguments #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE BangPatterns #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Word.Adler32 (
+
+	A, fromWord32, toWord32, step, initial
+
+	) where
+
+import Prelude hiding (uncurry)
+import Data.Bits
+import Data.Word
+
+step :: (Int, A) -> Word8 -> (Int, A)
+step (n, A a b) w = case n of
+	0 -> (5551, A (( a + fromIntegral w) `mod` 65521) ((b + a + fromIntegral w) `mod` 65521))
+	_ -> (n - 1, A (a + fromIntegral w) (b + a + fromIntegral w))
+
+data A = A !Word32 !Word32 deriving (Show, Eq)
+
+initial :: A
+initial = A 1 0
+
+fromWord32 :: Word32 -> A
+fromWord32 w = A (w .&. 0xffff) (w `shiftR` 16)
+
+toWord32 :: A -> Word32
+toWord32 = uncurry (.|.) . first (`mod` 65521) . second ((`shiftL` 16) . (`mod` 65521))
+
+first :: (Word32 -> Word32) -> A -> A
+first f (A a b) = A (f a) b
+
+second :: (Word32 -> Word32) -> A -> A
+second f (A a b) = A a (f b)
+
+uncurry :: (Word32 -> Word32 -> a) -> A -> a
+uncurry f (A a b) = f a b
diff --git a/tools-yj.cabal b/tools-yj.cabal
--- a/tools-yj.cabal
+++ b/tools-yj.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           tools-yj
-version:        0.1.0.36
+version:        0.1.0.37
 synopsis:       Tribial tools
 description:    Please see the README on GitHub at <https://github.com/YoshikuniJujo/tools-yj#readme>
 category:       Tools
@@ -44,6 +44,7 @@
       Data.Sequences.ToolsYj
       Data.Text.ToolsYj
       Data.Tuple.ToolsYj
+      Data.Word.Adler32
       Data.Word.Crc32
       Text.Show.ToolsYj
   other-modules: