An image forming apparatus having a drawer unit that includes therein a paper-feeding conveying path for conveying a recording medium conveyed from a paper feeding unit on which the recording media are stacked to an image forming unit and/or a discharge conveying path for conveying the recording medium on which an image has been formed to a discharging unit, and be drawn out from an apparatus main body; a lock unit that locks the drawer unit to the apparatus main body; a straddle detecting unit that detects whether the recording medium straddles a conveying path in the apparatus main body and a conveying path in the drawer unit; and a controller that controls the lock unit to lock the drawer unit to the apparatus main body when the straddle detecting unit detects the straddle.