Provided in the present invention is a quinoline derivative for treating gastric cancer. 1-[[[4-(4-fluoro-2-methyl-1 H-indol-5-yl)oxy-6-methoxyquinolin-7-yl]oxy]methyl]cyclopropylamine or a pharmaceutically acceptable salt, a hydrate or a prodrug thereof as provided in the present application can effectively treat gastric cancer, and can stabilize or relieve the state of illness of a gastric cancer patient.