The present invention provides an image forming apparatus including a first image forming unit for forming an image on a recording material at a first image forming position, a second image forming unit for forming an image on the recording material at a second image forming position different from the first image forming position, a light permeable recording material bearing member for bearing the recording material and for conveying the recording material to the first and second positions, a position detecting unit for detecting a position of a test pattern formed on the recording material bearing member by the first and second image forming unit, and a light reflecting member adapted to reflect light passed through the recording material bearing member onto the position detecting unit and shiftable to a position where the light is not reflected onto the position detecting unit.