PROBLEM TO BE SOLVED: To provide a novel gastric ulcer preventive having high gastric mucosa protective action and high level of safety.SOLUTION: A gastric ulcer preventive comprises 0.005 mass%-50 mass% of a copolymer of 2-methacryloyloxy ethyl phosphorylcholine and butyl (meth)acrylate with a weight average molecular weight of 10,000-10,000,000 as an active ingredient.