Disclosed is a benzothiophene oxide derivative represented by the generalformula (wherein R1 and R2 are the same or different and each represents oneor more groupsselected from a hydrogen atom, a halogen atom, an alkyl group, an aryl group,an aralkyl group,an alkoxy group, an aryloxy group, an alkenyl group, an amino group, aheterocyclic group, anamino group, a hydroxyl group, a carboxyl group, an oxo group and the like； R3represents analkylamino group, an amino group, a hydroxyl group or the like； and m and nare the same ordifferent and each represents an integer of 1-6) or a salt thereof, which isuseful as a prodrug of abenzothiophene derivative or a salt thereof.
