An image forming apparatus is configured to include an apparatus main body, further including an internal sheet discharge portion for ejection of a sheet having an image formed thereon; and a relay conveying unit, positioned in the internal sheet discharge portion, and configured to convey the sheet to a post-processing device. The relay conveying unit has: a body portion; a cover member positioned on a side surface of the body portion; a detection switch; and a hook positioned on the cover member. The body portion and cover member form a sheet conveying path, the cover member being turnable in vertical directions into opening and closing states, to open and form the sheet conveying path, respectively, as detected by the detection switch. The hook prevents the cover member from being turned from the closing state and switches the detection switch into an on state.