Abstract: A linear actuator has a clutch mechanism settled between a worm gear and a screw of the linear actuator. The clutch mechanism including a disc spring normally stays in a clutched position where a driving power is transmitted from the worm gear to the screw. When the linear actuator is overloaded, the clutch mechanism changes to a declutched position by compressing the disc spring so that the driving power is not transmitted to the screw. Thereby, the clutch mechanism protects internal components of the linear actuator from being damaged, thereby improving durability of the linear actuator.