A drive device includes a drive source, a drive train including a plurality of drive transmitters, and a positioning member. The drive train transmits a driving force of the drive source to a driven member. The plurality of drive transmitters include a first group of the drive transmitters and a second group of the drive transmitters. The drive source and the first group of the drive transmitters together serve as an integrated unit attached to one side of a facing member facing a side panel of an image forming apparatus. The integrated unit includes a positioning object. The second group of the drive transmitters is supported by a shaft disposed on another side of the facing member. The positioning member includes a positioning portion with which the positioning object is engaged on the one side or said another side of the facing member.