Abstract: An actuator AE1 includes a lock mechanism R1 configured to fill a gas G generated by operating a gas generator 35 at inside of a cylinder 22 and moving forward a piston 38 along with a support rod 40 for restricting a rearward movement of the support rod moved forward. The support rod 40 is arranged to be able to absorb a kinetic energy of a protection object person and capable of being plastically deformed when the protection object person is received by a receiving member after having been moved forward. A lock mechanism R1 is constituted by a diameter enlarging deformed portion 42 arranged at a piston and a locking stepped portion 24 capable of restricting the rearward movement of the piston.