A drug for hepatic diseases, particularly an ameliorant for hepatic functions and a drug for hepatitis, containing docosahexaenoic acid or a derivative thereof (DHA) as an active ingredient. The DHA as the active drug ingredient, though also taking part in the metabolism of cholesterol formed in vivo and exuding into the plasma, mainly metabolizes that cholesterol specifically which is accumulated in hepatic microsomes as a result of hypometabolism or dysbolism to thereby bring about the recovery of flexibility of a microsome lipid membrane, thus enhancing the enzymatic activity, and to significantly reduce a triglyceride, thus being prospective as an ameliorant for hepatic functions in treating fatty liver, hepatic cirrhosis, etc. The invention also provides a drug for hepatitis, which can inhibit the induction of hepatitis which is one of the factor causative of chronic hepatitis, hepatocirrhosis, hepatocellular carcinoma, hepatic insufficiency, etc.