The present invention provides Hsp90 family protein inhibitors comprising, as an active ingredient, a benzoyl compound represented by general formula (I): (wherein n represents an integer of 0 to 10; R1 represents substituted or unsubstituted lower alkoxy, substituted or unsubstituted lower alkoxycarbonyl, CONR7R8 or the like; R2 represents substituted or unsubstituted aryl, a substituted or unsubstituted aromatic heterocyclic group or the like; R3 and R5, which may be the same or different, each represent a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted lower alkenyl or the like; and R4 and R6, which may be the same or different, each represent a hydrogen atom, halogen, substituted or unsubstituted lower alkyl, substituted or unsubstituted aryl or the like) or a prodrug thereof, or a pharmaceutically acceptable salt of said benzoyl compound or said prodrug.