An object of the present invention is to provide a therapeutic agent for ulcerative colitis which allows 5-aminosalicylic acid (5-ASA) useful as a therapeutic agent for ulcerative colitis to be efficiently delivered to the large intestine of the affected site almost without being absorbed or metabolized in the stomach or the upper part of the small intestine and is safe and can be administered over a long term. The present invention relates to 5-ASA into which D-galactose represented by the following general formula [1] has been introduced. The compound of the present invention can be efficiently delivered to the large intestine of the site of action, and is degraded by the intestinal bacterial flora, whereby 5-ASA as the active ingredient can be produced in the large intestine.