Processes for preparing 1-benzyl-4-[(5,6-dimethoxy-lindanon)-2-yl]methylpiperidine (donepezil), which is useful as an intermediate for medicines, and for producing 1-benzyl-4-[(5,6-dimethoxy-1-indanon)-2-yl]methylpiperidine hydrochloride (donepezil hydrochloride), which is useful as a medicine. The process for donepezil hydrochloride production comprises catalytically hydrogenating the compound represented by the structural formula (III) [1-benzyl-4-[(5,6-dimethoxy-lindanon)-2-ylidene]methylpiperidine] with a Raney nickel catalyst under mild conditions and subsequently treating it with hydrochloric acid. Thus, impurities are further diminished. The operations are simple and the process is suitable for industrial production.