Provided is a method for producing a piperidin-4-one derivative useful as an intermediate for agricultural chemicals or pharmaceutical products. A piperidin-4-one derivative represented by formula (III-a) or formula (III-b) is produced by reacting a cyclic bis(aminol)ether compound represented by formula (I) and an acetone derivative represented by formula (II) in the presence of at least one substance selected from the group consisting of protonic acids, Lewis acids, acid halides and dialkyl sulfuric acids.