An optical scanning apparatus includes a light source which emits optical beam; a light deflector which deflects the optical beam from the light source in a main scanning direction; an optical system which leads the optical beam from the light deflector to a scanned surface; and an optical sensor equipped with a light-receiving part to receive the optical beam from the light deflector excluding a part of the optical beam which falls in an effective exposure area of the scanned surface and used to control scan timing; and a holding member which holds the optical sensor with the light-receiving part tilted at a predetermined angle with respect to the main scanning direction.