To provide a unit valve for purification layer, which is screwed on a water cartridge or the spout of a PET bottle by a screw part on the inner wall of the periphery of a cylindrical body, through which purified water is flowed out into a water receptacle by opening the valve by inserting the valve on the water cartridge or the PET bottle to the water receptacle, and which is closed by detaching the valve.

The unit valve is a two-layered object having the screw part on the inner wall of the periphery of the cylindrical body, and has a purification function by providing a purification layer such as an active carbon fiber filter, an ion-exchange resin, Cellgaia, or a fiber dust filter in the inner wall of the cylindrical body. A hole is made on the center of the purification layer, a switching valve axis with a spring wound is inserted on the hole so that it is operated together with a silicon valve at the rear part, the valve is screwed on the spout of the water cartridge with the screw part of the cylindrical body, the water receptacle to which the water cartridge is fixed, is provided, and the valve is opened by inserting the valve on the cartridge to flow out water and is closed by detaching the valve.