SEAT RECLINING DEVICE FOR VEHICLE

An engagement section of a pole and a protruding section of an upper arm restrict movement of the pole outward in the radial direction and disable meshing of outer teeth and inner teeth, when the relative rotation angle of a lower arm and the upper arm is within a prescribed range. Outer teeth and the inner teeth of poles cannot engage as a result of the restriction on movement of the pole outward in the radial direction. The amount of movement by the poles separating from the inner teeth along the radial direction is set so as to be greater than the amount of movement by the pole separating from the inner teeth along the radial direction, when the pole reaches a position corresponding to where the outer teeth and the inner teeth cannot mesh as a result of the protruding section, etc., during the unlock operation.