Disclosed is a piperidine derivative represented by the general formula (I) below or a salt thereof. Also disclosed is an antioxidant containing such a compound or a salt thereof as an active constituent. (I) (In the formula, R1 represents an alkyl group having 1-8 carbon atoms or the like; R2 represents a hydrogen atom, an alkyl group having 1-8 carbon atoms, an alkylcarbonyl group having 2-8 carbon atoms or the like; and R3 and R4 may be the same or different and represent alkyl groups having 1-8 carbon atoms or the like.)
