Abstract: A pressurized water supply system for a dental unit-chair comprising a water purifier purifying or sterilizing water from a water supply source, and supplying the water to which a given pressure is applied to a medical instrument instrument. A pressurized water supply device for a dental unit-chair includes a case, an inflow tube provided to the case and connected to a water supply source, a pump installed within the case and connected to the inflow tube to jet out the water from the water supply source under a given pressure, a water purifier provided to the case in multi-stage and removing various alien substances, chemical substances, heavy metals, ions, germs, etc. from the water supplied from the pump, and A pressurized water supply tube provided to the case, connected with the water purifier, and connected to a medical instrument installed on the dental unit-chair, thus providing the compressed water thereto.