The present invention relates to a unit chair and, more specifically, to a unit chair including a link part capable of adjusting the angle of a headrest. In a unit chair according to one embodiment of the present invention, the link part comprises: a first link member fixed to a backrest of the unit chair； a first link shaft； and a second link member of which one end portion is linked to the first link member by means of the first link shaft so as to be rotatable around the central axis of the first link shaft, wherein a plurality of first ratchet grooves aligned in an annular shape around the central axis of the first link shaft are formed on one surface of the first link shaft, and the second link member can include: a first elastic member； a plurality of first pins, which are aligned in an annular shape, are supported by means of the first elastic member, and are fastened to the first ratchet grooves by means of the restoring force of the first elastic member so as to prevent one-way rotation of the second link member； and a releasing part for transmitting external force to the elastic member when the external force is applied, so as to release the engagement of the first ratchet groove and the first pin, and enabling the bidirectional rotation of the second link member.La présente invention concerne une chaise unitaire et, plus précisément, une chaise unitaire comprenant une partie de liaison capable d'ajuster l'angle d'un appui-tête. Dans une chaise unitaire selon un mode de réalisation de la présente invention, la partie de liaison comprend : un premier élément de liaison fixé à un dossier de la chaise unitaire ； une première tige de liaison ； un second élément de liaison dont une partie d'extrémité est liée au premier élément de liaison à l'aide de la première tige de liaison afin de pouvoir tourner autour de l'axe central de la première tige de liaison, une pluralité de premières rainures de cliquet alignées sous une forme annulaire autour de l'axe central d
