Gastric ulcer is a disease disorder caused by damage to the mucous layer, submucosa, to the muscle layer of the gastrointestinal tract due to the activity of pepsin and stomach acid. This study aims to determine the effect of nutmeg flesh as an anti-ulcer. Tests were carried out using Wistar strain white rats. Nutmeg Flesh Extract (NFE) was obtained by maceration method using 70% ethanol, then divided into three dose groups, NFE 400, 900, and 1800mg/kgbw. Acetosal 500mg/kgbw was given as an ulcer inducer on the 8th day. As a positive control, Omeprazole was used at 20 mg/Kgbw. The test parameters observed were the number of ulcers, ulcer index, % protection, gastric pH, total acidity of gastric juice, and histology of gastric tissue. The results showed that the ethanol extract of nutmeg flesh at doses of 450, 900, and 1800 mg/kgbw had significantly different anti-ulcer activity against negative controls (p<0.05) in acetocal-induced rats with the highest protective ratio indicated by a dose of 1800 mg/Kgbw.