An electrophotographic image forming apparatus includes a drum cartridge with an image bearing drum and charger for charging a surface of the drum. The apparatus further includes a rotary supporting a plurality of developing devices each having a developer carrying member for developing an electrostatic latent image formed on the drum, with the rotary being swingably mounted to the main assembly through a supporting member and being rotatable, relative to the supporting member, to bring the developing device to a developing position for developing the latent image. A locking member is provided for spacing between the developing device positioned in the developing position and the image bearing member, the locking member being demountably mounted between the drum cartridge and the rotary, and the locking member being effective to prevent an urging member from moving from a position urging the drum cartridge to the main assembly.