To prevent the breaking the balance of a nose/knee position which is supposed to be the most comfortable position, to solve the problems of deviation of the head or the back of a patient and coming-off of slippers by providing a dental treatment chair with a structure executing a similar operation to that of an easy chair.

A dental treatment chair body 10 comprises a headrest 1, a backrest 2, a contour seat 3, a legrest 4, a footrest 5 and the like. The contour seat 3 is supported on a base 20 by lifting mechanisms 111 and 112 vertically movably supporting the seat at two front/rear positions independently, respectively. The lifting mechanisms 111 and 112 independently vertically move, respectively, so that the treatment chair body 10 can be changed into a state shown in Figure (A) or a state shown in Figure (B) without changing the form of the treatment chair 10.