An optical scanning apparatus includes a light source for emitting a beam in accordance with image information; a controller substrate for controlling the light source; a deflector for scanningly deflecting the beam; an optical device for directing the deflected beam onto a member-to-be-scanned; a casing supporting the substrate, the deflector and the optical device, wherein the substrate is provided with a projected portion projecting relative to the casing; and a connector for removably connecting a cable for supplying a signal to the light source, the connector being provided on a side of the projected portion where the controller substrate is supported by the casing. The cable is insertable and removable relative to the connector in a direction parallel with a surface of the projected portion provided with the connector.