in an image forming apparatus wherein developer images formed by an electrostatic image on an image bearing member being developed by the use of a developing apparatus which has a moving member holding a plurality of developing devices having developers of different colors therein and capable of selectively moving the developing devices to a developing position , and in which during the moving operation of each developing device to the developing position , the moving distance of at least one developing device differs from the moving distance of the other developing devices , when the moving operation is performed during an ordinary image forming operation , the movement of the moving member is controlled so that the position of an image forming region on the image bearing member when the at least one developing device has arrived at the developing position and the position of the image forming region on the image bearing member when the other developing devices have arrived at the developing position may become substantially equal to each other .