An image forming apparatus includes: an image forming unit for forming successive images and a pattern image with developer on a transfer member, the successive images including a first image and at least one second image subsequent to the first image; a conveying unit for conveying a medium; a transfer unit for transferring the successive images on the transfer member onto the medium; a detector for detecting the pattern image on the transfer member; a controller for causing the image forming unit to form the pattern image between the first image and the at least one second image and form the at least one second image on the transfer member based on the detection of the pattern image by the detector; and a separation unit for separating the transfer member and the medium from each other to prevent the pattern image from being transferred onto the medium.