To provide an image forming apparatus including: a discharge tray which can moves between a first position capable of loading a discharged sheet and a second position that is separated from the first position; and a sheet loading amount detection sensor which has a sheet detection flag abutting against the upper surface of the sheet loaded on the discharge tray and capable of moving in accordance with a loading amount of the sheet loaded on the discharge tray, and detects the sheet loading amount by detecting a position of the sheet detection flag, wherein when the discharge tray means is located at the second position, the sheet detection flag is removed from a position capable of detecting the sheet loading amount.