To easily regulate driving power supplied to an instrument, by making long a stroke of pushing down a cover plate member, in a dental treatment chair using the cover plate member for covering a pedestal of the dental treatment chair, as a foot controller.

The dental treatment chair includes the cover plate member 11 arranged on the pedestal 10 of the dental treatment chair 1 and pushed down by a foot operation, the dental treatment instrument 7 is driven by pushing down the cover plate member 11 by the foot operation, and the driving power supplied to the instrument 7 is controlled in response to a push-down amount of the cover plate member 11. A foot operation plate 12 is provided to be extended forward from the cover plate member 11 and to be rotatable around a shaft 13 as the center on the cover plate member 11, in an upper part of the cover plate member 11, and a rotational number or the like of the instrument 7 is controlled by pushing down the foot operation plate 12. The driving power is controlled easily since a stroke of the foot operation plate 12 is larger than the push-down stoke of the cover plate member 11.