An image forming apparatus which allows an independent and easy replacement of replaceable image forming devices including an image forming unit detachably provided in the image forming apparatus. The image forming unit includes a housing, a plurality of replaceable devices, and a nonvolatile memory. The plurality of replaceable devices are replaceably mounted inside the housing. The nonvolatile memory is mounted on the housing and stores lifetime information of the image forming unit and each one of the plurality of replaceable devices.