An opening/closing detection mechanism has a multifunctional peripheral body portion, a front cover, a side cover, and an interlock mechanism. The interlock mechanism contains a switch, a plate-like portion, a bulged portion, and a rocking mechanism. The bulged portion is provided on the side cover. When the side cover is in the closed state, the bulged portion abuts on a rear region located on the side opposite to the front cover with respect to a region where a projection portion is provided of the switch. The rocking mechanism rocks the switch in the opening/closing direction of the front cover according to the opened/closed state of the side cover.