There is provided a novel method for producing an optically active (4R)-1,3-thiazolidine-4-carboxylic acid by allowing cells of a microorganism or a preparation obtained from cells of a microorganism having activity for stereoselectively hydrolyzing an optically active (4R)-1,3-thiazolidine-4-carboxylic acid amide to act on a mixture of (4R)- and (4S)-enantiomers of a 1,3-thiazolidine-4-carboxylic acid amide to produce the optically active (4R)-1,3-thiazolidine-4-carboxylic acid and separating the optically active (4R)-1,3-thiazolidine-4-carboxylic acid.