To provide a chlorine dosing and pressure supplying device for dental city water which is simple and can add chlorine of a controlled amount.

The chlorine dosing and pressure supplying device 10 for the dental city water which maintains the satirizing power of the city water for dental treatment by dosing the chlorine to the city water has a pipeline for regulating the flow rate of the city water supplied from the city water supply piping 3 and a chlorine dosing cylinder 15 which a disposed in mid-way of the pipeline and in which a chlorine ion additive is housed. The chlorine dosing cylinder 15 has a cylinder having a hole disposed in the lower part and an annular body having a notch arranged on the outer side of the cylinder and the opening area of the hole is changed by relatively turning the cylinder and the annular body.