To provide a linear actuator with an oiling mechanism stable in operation, capable of being reduced in cost, and of automatically feeding a lubricant to a threadedly meeting surface between a screw shaft and a nut.

In a linear actuator attached with an oiling mechanism, formed out of a screw shaft 4 to be drivingly rotated, a ball screw nut 6 to be linearly moved in the axial direction when the nut is threadedly met with the screw shaft 4 so as to let the screw shaft 4 be drivingly rotated, and of a rod 8 to be linearly moved in the axial direction together with the ball screw nut 6 while being mounted to the ball screw nut 6, the oiling mechanism 20 is formed out of an oil impregnation ring 22 composed of two segments 22A in the inner circumferential surface of which no screw groove is formed, a cylindrical holder 24 supporting the two segments 22A inside, a ring spring 26 pressing the inner circumferential surface 22B of the two segments 22A onto the outer circumferential surface 4A of the screw shaft 4, and of a pan small screw 28 holding the two segments 22A in the inside of the holder 24.