An N-acylpiperazine derivative or a salt thereof expressed by the following formula 1: ##STR1## wherein R.sub.1 represents a pyridylcarbonyloxy lower alkyl group, a benzoylamino lower alkyl group, benzyl group, carbamoyl group, pyridyl group, or diphenylmethyl group;R.sub.2 represents a lower alkyl group or a lower alkoxy group;n represents an integer of 0 to 2;R.sub.3 represents a hydrogen atom, an alkenyl group, or benzyl group; andm represents an integer of 1 to 3.The N-acylpiperazine derivative or a salt thereof has an anti-ulcer effect, an antibacterial activity against Helicobacter pyroli, and high safety to be available for prevention or cure of various ulcers.