To provide a reclining device having large locking strength and less backlash.

The reclining device is formed of a pair of first poles (main poles) 41 disposed at diagonal positions and at least one second pole (sub pole) 43. A first cam (cam unit) 31 moves poles to locking positions, and when external teeth 41a of the first pole 41 and an internal teeth 23 of a ratchet (first member) 21 are engaged without play, external teeth 43a of the second pole 43 and the internal teeth 23 of the ratchet 21 are engaged with play.