A chair (1), wherein a seat back frame (5) installed at the rear of a seating frame (4) is divided into a seat back upper frame (55) and a seat back lower frame (50) and at least the seat back upper frame (55) is tilted rearward through shafts (8) and (71) provided for tilting rearward the seat back upper frame (55), whereby a seating comfortableness can be improved.