An image forming apparatus includes a reader; an image former, provided below the reader, for forming an image on a sheet; a sheet discharge portion, provided between the reader and the image former, for discharging and stacking the sheet; an operating portion provided in a front side adjacent to the reader in the horizontal direction and slidable along a side of the reader; a sensor unit provided at a side of the reader in a outside of a slidable range of the operating portion, the sensor unit being can project a signal on the side of the reader and receiving a reflection wave of the signal to detect presence of the user in an area in the front side; and a controller for restoring a state of the apparatus from a sleeping state to a stand-by state in response to detection by the sensor unit.