An image forming apparatus includes a first conveying portion provided with a discharge opening, a second conveying portion, a switching unit switched between a first state in which a recording medium is guided to the first conveying portion and a second state in which the recording medium is guided to the second conveying portion, a detecting unit provided in the discharge opening and for detecting the recording medium, a controller for controlling the switching unit, and a discriminating unit for discriminating that the switching unit is abnormal in a case where after the switching unit is controlled by the controller so as to be switched to the second state, a time from a start of detection of the recording medium by the detecting unit to an end of the detection is within a predetermined period.