An image forming apparatus has a structure in which a toner image formed in an electrophotographic process is transferred from an intermediate transfer belt to a member to be transferred. The apparatus includes a secondary transfer roller that becomes a pressure contact state with respect to the intermediate transfer belt to make it perform a transfer process and can move between the pressure contact state and a separated state, and a press and separation driving device for driving the secondary transfer roller to become the pressure contact state and the separated state. The pressure contact state or the separated state of the secondary transfer roller is detected in accordance with a variation of an output of an IDC sensor for detecting a state of a bare surface of the intermediate transfer belt.