A vehicle seat including: a seat back including a top plate main part configured to support a body of a seated person from the rear side and a top plate side part configured to protrude more forward than the top plate main part to support the body of the seated person from the lateral side; a side adjuster configured to move the top plate side part between a protruding position in which the top plate side part protrudes more forward than the top plate main part and a retracted position in which the top plate side part is retracted from the protruding position; and a controller configured to, in a case where a side collision of a vehicle is detected, drive and control the side adjuster so that the top plate side part is in the protruding position.