Abstract: A support apparatus for supporting a user in a plurality of working positions includes a seat supported on a frame and a seat back connected to the frame for movement between a plurality of angular positions ranging between a horizontal position and an upright position. The seat back is positioned in any of the angular positions by a carriage which supports the seat back for pivotal movement about a horizontal axis and by a shifting structure which carries out translational movement of the seat back relative to the pivot axis during pivoting movement of the seat back. The shifting structure shifts the seat back toward the seat during pivotal movement toward the horizontal position and away from the seat during pivotal movement toward the upright position so that the positional relationship between the seat back and the back of a user is preserved.