We have investigated the effect of concentrated apyrase derived from potato on experimental-induced stress ulcer. A total of 24 female Wistar Albino rats were applied to immobilization stress for 20 hours. While the control group was only given physiological serum, the first experimental group was administered 100 mg/kg apyrase and the second group, 200 mg/kg apyrase, intravenously. After stress was induced, the stomachs of the rats were removed and opened along the major curvature. The scores of ulcers were calculated by examining the gastric mucosa, and the gastric tissue was also evaluated histopathologically. As a result, it was observed that 200 mg/kg apyrase prevented the development of stress ulcer whereas 100 mg/kg apyrase did not.