PURPOSE: To improve the safety by executing freely angle adjustment by only one side of coupling parts of both sides of a seat frame and a back frame of the reclining seat, and locking its turning by the coupling part of the opposite side at the time of generation of a large load.

CONSTITUTION: The reclining seat is formed by covering a seat cushion frame 1 and a seat back frame 2 with a seat member. The frames 1 and 2 are coupled to a recliner device 3 by an emergency lock type hinge device 4 of the opposite side. Usually, by operating only a handle of the recliner device 3, an inclination angle of a back rest is set to a desired inclination angle. When a large load is generated due to an emergency start, a sudden brake, etc., a fixed hinge member 10 fixed to a base bracket 5 fixed to the frame 1 constituting the emergency lock type hinge device 4 and an eccentric member attached to a rotary shaft 20 connecting a movable hinge member 30 attached to the frame 2 lock mutual turning of both the hinge members 10 and 30. In such a way, the cost is reduced, and the safety is improved.