Vehicle seat

A vehicle seat (1) comprises: a seat body (2) including a seat bottom (4) and a seat back (5); a support device (3) provided in the seat body and configured to adjust supporting positions for supporting a lumbar region of an occupant; a pair of right and left seat back side frames (51) constituting right and left frames of the seat back; and at least one bladder (31A, 31B) configured to be inflatable and deflatable to change the supporting positions and arranged between the right and left seat back side frames and constituting the support device. The bladder (31 A, 31 B) comprises an air chamber (31 C) having a center portion and both end portions along a lateral direction, and the center portion of the air chamber has a portion which is thinner in thickness in the front-rear direction than the both end portions in an inflating state of the bladder.