To provide an actuator not to be overloaded and an optical axis adjusting device for a vehicular lighting fixture unit, which uses the actuator.

The actuator comprises a rod to be connected to the vehicular lighting fixture unit supported pivotally around a vertical or horizontal axis and an actuator body having a rod projecting port and holding the rod at least partly projecting from the rod projecting port while changing the amount of projection of the rod, wherein the rod contains a first rod and a second rod, with the first rod having one end portion to be connected to the vehicular lighting fixture unit and the other end portion connected with one end portion of the second rod such that the first rod can pivot on the second rod.