A seat reclining device in which reclining mechanisms (10A, 10B) disposed on both the right and left sides of a seat (1) are locked and unlocked in synchronism with each other by a connection member (20). A connection structure for connecting the connection member (20) to an operating shaft (16A) is formed in a transmission stopping structure capable of stopping the transmission of an unlock operation between the reclining mechanisms (10A, 10B) when the rotating displacement of a relative deviation therebetween to release a locked state occurs between the reclining mechanisms (10A, 10B) brought into synchronized rotating positions by the acting of deviated load on the right and left portions of a seat back (2) for which the reclining mechanisms (10A, 10B) are brought into a locked state.
