(26) An aminopeptidase N inhibitor according to (1), which comprises an N-phenylimide derivative represented by the general formula (I??????-1) or (I??????-2): wherein each of R1 and R2 is a hydrogen atom, a lower alkyl group, a lower alkoxy group or a lower alkylthio group, Y is an oxygen atom or a sulfur atom, each of X1 and X2 is a halogen atom, a nitro group, a cyano group, a trifluoromethyl g