Optical axis adjusting screw

An optical axis adjusting screw (15) is provided with a shaft portion (16), a gear portion (17), and an elastic engagement portion (18). The elastic engagement portion (18) is provided with a base end and a free end. The base end is fixed to the shaft portion (16). A distal end face (18a) is formed at the free end and is substantially perpendicular to an axial direction of the shaft portion (16). There is no parting line on the distal end face (18a).