Examination of the sizes of gastric mucosal injury has been conducted by visual means. However, the human visual-eye examination may sometimes involve personal biases and errors. In order to reduce these errors, automated analytical apparatuses have been developed. The equipment is generally expensive. In the present study, a low-cost imaging analytical method to examine the antiulcer action of drugs is reported. By using our imaging analytical method, an antiulcer effect of herbal medicine was examined on hydrochloric acid-ethanol induced gastric mucosal injury. Acetone extract of Atractylodis Rhizoma was found to have antiulcer action. In addition, the examination of fractions of the acetone extract, obtained through column chromatography, indicated that atractylon, at 17.5 mg/kg, p.o. significantly inhibits gastric mucosal injury.