An image forming apparatus includes a main body and a fixing unit, as well as first and second fixing unit attachment detection portions, each of which includes an optical sensor. The fixing unit is detachably attached to the main body, and includes a unit-side connector which connects with a main body-side connector when the fixing unit is attached to the main body to receive power. The first fixing unit attachment detection portion is at a different position on the main body from where the main body-side connector is located in a longitudinal direction of the fixing unit. The second fixing unit attachment detection portion is at a different position on the main body from where the main body-side connector is located and a position where the first fixing unit attachment detection portion is disposed in the longitudinal direction of the fixing unit.