SEAT RECLINING DEVICE

PROBLEM TO BE SOLVED: To provide a seat reclining device capable of reducing the risk that the movement of a lock member to a base plate is not smooth due to welding head applied between a welding projection and a holding part in spite of a structure in which a welding projection fitted to a holding part formed by a hole formed on one of a seat cushion side frame and a seat back side frame is projected on the outside surface of a base plate movably supporting a lock member on the inside surface.SOLUTION: A seat reclining device includes: a rotary cam 47 turned between a lock position for locating lock members 36, 37 at a meshing position and an unlock position for locating the lock members at a non-meshing position; and a welding projection 33 projected on the outside surface of a base plate 27 and fitted to a holding part including a through hole or a blind hole formed on one of a seat cushion side frame 13 and a seat back side frame 16. The welding projection has a part to be welded located at the outer peripheral side of the base plate from an external tooth of the lock member located at the meshing position, and welding W1 is applied to range from the part to be welded to the peripheral edge part of the holding part.