To raise the headrest of a chair in relation to the backrest thereof, and make it possible for the line of sight of a seated person to be oriented forward, in the case of wanting to orient the line of sight forward when slightly reclining the backrest of the chair from an upright position, and to recline the headrest of the chair in relation to the backrest, in the case of wanting to significantly recline the backrest and attain a sleeping posture, a chair is configured in the following manner: the chair has a reclinable/straightenable back frame (8), and a head frame (22) that is reclinable/straightenable in relation to the back frame (8); the head frame (22) rises in relation to the back frame (8) as the back frame (8) reclines from the upright position, but after the angle (a) of the front surface of the head frame in relation to the vertical axis of the back frame reaches a prescribed angle, the head frame (22) reclines in relation to the back frame (8) as the back frame (8) reclines further; in addition, the head frame (22) rises in relation to the back frame (8) as the back frame (8) rises from the reclined position, but after the angle (a) reaches the prescribed angle, the head frame (22) reclines in relation to the back frame (8) as the back frame (8) rises further.