An image forming apparatus which can control to turn on/off a light emitting element depending on a sheet state on a manual sheet tray is provided. The image forming apparatus includes the manual feed tray on which the sheet is placed. The image forming apparatus is configured to be switchable between normal power mode and power saving mode. In the normal power mode, normal power is supplied. In the power saving mode, less power is consumed as compared to the power consumed in the normal power mode. The image forming apparatus includes a manual sheet feeding sensor which detects presence/absence of the sheet on the manual feed tray. The image forming apparatus includes a sheet length sensor S and a sheet length sensor L which include the light emitting element and a light receiving element to detect approximate sheet length of sheet placed on the manual feed tray in a conveying direction.