In an image forming apparatus, a module box moves between a first position and a second position. A locking/unlocking unit locks the module box into the first position, and a biasing unit biases the module box from the first position to the second position when the locking/unlocking unit is unlocked. Object components (such as developer cartridges, or intermediate transfer belt assemblys) are detachably installed in the module box. By using the module box, these heavy and bulky object components can be easily installed and removed, allowing easy repair and maintenance. Further, the components can be protected from damage during installation and detachment, and the user can use the image forming apparatus more conveniently.