To prevent a cap member for centering for retaining the relative rotating positions of a hinge pin and a connection rod of a reclining device neutral from being affected by welding heat, etc.

In the reclining device, the hinge pin 16 is inserted into a tubular connection rod 26, and the hinge pin and the connecting rod are connected to each other in the centered state with the relative rotating positions retained neutral. Both hinge pin 16 and the connection rod 26 are polygonal so that the rotation can be transmitted. The tubular cap member 30 for centering is press-fitted into the outer circumference of an end of the connection rod. The cap member 30 has an insertion hole 32 into which the hinge pin 16 is inserted. The rotating position of the cap member 30 relative to the connection rod is determined with a polygonal face of the outer circumference of the connection rod 26 as the reference, and the rotating position of the hinge pin 15 relative to the connection rod 26 is determined by the insertion hole 32.