To provide an image forming apparatus preventing an occurrence of an abnormal image such as transfer misalignment or transfer void by maintaining high accuracy in position between an image carrier and a registration roller and between pre-transferring guides with a simple composition.

The image forming apparatus supplies the paper that is fed by a registration roller 12 from a paper supplying means to a transferring section between a photoreceptor drum (image carrier) 6 that is provided in a drum unit 11 which is insertable to/extractable from a body frame 101 in a perpendicular direction and a facing transfer roller (transferring means) through a pre-transfer guide 13 and transfers a toner image formed on the photoreceptor drum 6 onto the paper. In this case, an alignment holder 19 with respective alignment means (alignment boss 21, etc.) of the drum unit 11, the registration roller 12 and the pre-transferring guides 13 is attached to the body frame 101 on the insertion side of the drum unit.