An image forming apparatus includes an image bearing member, image forming station for forming a latent image on the image bearing member, a conveying passage extending toward the image bearing member to guide a developing device, a first moving mechanism for engaging with the developing device in the conveying passage and moving it in a substantially horizontal plane, wherein the image bearing member, the latent image forming station, the conveying passage and the first moving mechanism are provided in a main body of the image forming apparatus, a device for accommodating a plurality of developing devices. The accommodating device is mounted to the main body, the accommodating device includes, a second moving mechanism for moving the developing device opposed to the conveying passage into the conveying passage in a substantially horizontal plane and an accommodating case having partition stages arranged substantially vertically for accommodating plural developing devices and movable together with the developing devices accommodated therein, and a driver for transmitting a driving force selectively to the first driving mechanism, the second driving mechanism and the accommodating case.