To move a treatment chair to an expected position as quickly as possible without giving a feeling of fear to a patient.

A dental chair has a back rest and a contour seat, and at dental treatment time, the back rest is raised up and brought down, and dental treatment is performed in a falling-down condition, and a gargle or the like is performed in a rising-up condition. A motor to raise up and bring down the back rest and a control means to control rotating speed of the motor are provided, and when the back rest is raised up and brought down, at first, it is slowly moved (T0 to T1), and next, it is move at fast speed (T1 to T2, and lastly, it is slowly moved (T2 to T3), and a shock is not given to a patient at starting-stopping time. Speed patterns (A, B, C and D) are made selectable by the patient according to a handicapped person, an aged person, a woman, a healthy strong person or the like.