PURPOSE: To prevent water spitted out by a patient from being scattered by providing a supporting block at a water supply/drainage unit so as to support a glass stand and a spitoon and movably supporting them within an almost horizontal plane.

CONSTITUTION: A water supply/drainage unit 2 arranged on the side of the position of a chair 1 is provided with a supporting block 3 equipped with a glass stand 31 for placing a glass for gargle, water supply pipe 32 for supplying water to the glass and spitoon 33, and supported by a stand 4 fixed on the floor. On the other hand, an instrument tray 6 is supported through an arm 5 to a bracket 1C fitted to the chair 1. The supporting block 3 turnably supports the stand 4 at the end part on the side, where the glass stand 31 is placed, with an almost perpendicular core as a center and the spitoon 33 is disposed at a certain position away from the glass stand 31. When the patient gargles, the supporting block 2 turns the stand at a suitable angle with the end part on the side of the glass stand 31 as a center and almost horizontally moves the spitoon 33 to the front position of the patient.