In a conventional vehicle seat with a reclining mechanism, a reclining unit is bolted to a seat frame. Consequently, a plate thickness has to be increased in order to ensure strength and a fastening bolt is required, producing factor which increases the number of parts. In order to solve the abovementioned problem, this vehicle seat with a reclining mechanism is configured such that a reclining unit (2) which has the reclining mechanism (5) is affixed to a back side frame (3) and a cushion side frame (40), which constitute the seat frame of the vehicle seat. The reclining unit (2) has the reclining mechanism (5), a movable bracket (6) which is affixed to the back side frame (3), and a stationary bracket (7) which is affixed to the cushion side frame (40). The reclining unit (2) is configured such that the reclining unit (2) is affixed to the back side frame (3) through the movable bracket (6) by welding and is fastened to the cushion side frame (40) by a bolt through the stationary bracket (7).