PURPOSE: To adjust the position of the subject dental treatment chair in a memory position and to more easily move the chair between a treatment position and a gargling position and adjust the treatment position by providing a switch arranged for the chair or the neighborhood of the chair and turning on the switch.

CONSTITUTION: When the above-mentioned switch 1 is pressed at a point where a patient is under a reference position state before the patient sits in the treatment chair, the chair moves to the memory position, namely, the treatment position. When this switch 1 is pressed in the memory position, the chair moves to the gargling position (the height of the seat of the chair is kept as it is, and the back tilt of the chair is returned), and a state in which the patient can gargle is obtained. When this switch 1 is pressed in the gargling position, the chair moves to the memory position. Consequently, when the above-mentioned switch 1 is pressed after that, the chair returns to the gargling position, and when the above-mentioned switch 1 is pressed next, the chair returns to the memory position again. Since the chair repeatedly moves between the treatment position and the gargling position in this manner only by pressing the single switch, the chair can be operated extremely easily, and an operator can concentrate on treatment for that amount.