A developing apparatus for developing an electrostatic image on an image bearing member includes a rotary member including a plurality of mounting portions, to which a plurality of developing devices and a plurality of balance weights are detachably mountable. The rotary member selectively shifts a mounted developing device to a developing position opposite to the image bearing member. A developing process is performed in a first mode in which developing devices are attached to all the mounting portions, and in a second mode in which a developing device is mounted to at least one of the mounting portions, and no developing devices are mounted to the remaining mounting portions, and wherein, in the second mode, balance weights are mounted to the remaining mounting portions. An image forming apparatus includes an image bearing member and the developing apparatus.