An image forming apparatus is disclosed that holds its detachably attached constituent units at predetermined positions for operations, and releases the hold when exchanging and inspecting the constituent units. The image forming apparatus includes a main body having an opened portion on one side, one or more devices detachably attached to the main body through the opened portion, and a holding unit that is capable of being opened and closed relative to the opened portion. The holding unit is engaged with the devices and holds the devices at the predetermined positions when the holding unit is closed relative to the opened portion. A fixing unit arranged on the holding unit fixes the holding unit when the holding unit is closed.