In a vehicle seat (car seat 1) including a first seat portion (seat cushion 10) movable between a use position and a retracted position, and a second seat portion (seat back 20) movable between a use position and a retracted position, an actuator mechanism is configured to cause the second seat portion to start moving toward its retracted position at a time when the first seat portion passes a predetermined intermediate position that is on a way from the use position toward the retracted position. In one embodiment, the actuator mechanism includes a biasing member (torsion spring 13, 23) configured to bias each of the seat cushion 10 and the seat back 20 from the use position toward the retracted position, a lock member (lock arm 42) configured to lock the seat back 20 in the use position, and an unlock device (cable 44, 42A) configured to release the lock member to cause the seat back 20 to start moving toward the retracted position, at a time when the seat cushion 10 passes the predetermined intermediate position that is on the way from a posture in which the seat cushion is ready for use toward a posture in which the seat cushion 10 is tipped up.