An optical scanning apparatus which includes: a light source unit which emits a light beam; a deflection scanning device which deflects the light beam emitted from the light source unit; an optical scanning unit having a scanning imaging lens and which scans a surface to be scanned; and a light beam detector which detects a position in a sub-scanning direction of the light beam, and is disposed in a position maintaining a correlation, in a time-varying characteristic, between an amount of change of a position in the sub-scanning direction of the light beam on the surface to be scanned and an amount of change of a position in the sub-scanning direction of the light beam detected by the light beam detector, in which a difference between the amount of change of the position in the sub-scanning direction of the light beam on the surface to be scanned and the amount of change of the position in the sub-scanning direction of the light beam detected by the light beam detector is equal to or less than a set value.