A seating posture is stabilized in such a manner that the shoulders of a passenger seated on a vehicle seat. A vehicle seat (S) is provided with a seat back (S1) configured to support the seated person from the rear. A shoulder support portion (Sa1) of the seat back (S1) configured to support a corresponding one of the shoulders of the seated passenger includes an air cell (10) configured to expand when air is supplied. When the air cell (10) expands, one end portion of the shoulder support portion (Sa1) on the outside in the width direction of the vehicle seat (S) moves more forward than the other end portion of the shoulder support portion (Sa1) on the inside in the width direction.