To accomplish a role of a mechanical fuse by bending it according to an element at the time of design and to impart a directivity thereto such that an output pin is not bent or broken by other factors by making the output pin as the mechanical fuse bendable only in one direction.

In the linear actuator, since an output pin 8a provided on a tip end of an output shaft 8 is bendable only in one direction by a shaft support portion 50, it is bent along one direction according to a design to obtain a mechanical fuse having one direction in the case where a failure is generated in a substance to be driven connected to the output pin 8a.