An image forming apparatus includes an operation unit receiving an instruction, and a connecting unit to which a wireless communication unit is detachably attached. The connecting unit is arranged at a bottom surface of a recessed portion formed on a back surface. The recessed portion has such a depth d that an indicator unit indicating a communicating state of a wireless communication unit, arranged on a surface of the wireless communication unit attached to the connecting unit, protrudes from the recessed portion. Thus, the possibility that a USB wireless LAN adaptor is damaged by external force or is erroneously pulled out can be reduced, the communicating state can easily be recognized visually, and thus, the USB wireless LAN adaptor can be used safely.