To provide a dentist's treatment chair which gives patient neither sense of uneasiness nor numbness even during a treatment taking a long time by constituting a counter seat, which is the part where body pressure is mostly applied when a patient sits or lie down, of a low repulsive and elastic material.

The dentist's treatment chair 10 having a back rest 12 and a counter seat 13 is used for dental treatment by raising or falling the back rest, whereas the counter seat 13 including the part, where the buttocks touch, is constituted of a low repulsive and elastic material 20. The low repulsive and elastic material 20 is inserted into a hollow portion 21a of a base member 21 of the counter seat, so that the counter seat may not be deformed.