The invention provides a valve disposed in a fluid supply path to control opening or closing of the supply path, configured to comprise, as components of the supply path, an inflow channel, a second channel, a first channel, and an outflow channel that are in communication with each other in sequence, in such a manner that fluid from a supply source entering the inflow channel passes through the second channel and the first channel in sequence and then flows out through the outflow channel. The valve further comprises a first valve piece and a second valve piece disposed movably in the first channel and the second channel respectively. Blocking or unblocking of the communication between the first channel and the outflow channel is controlled by movement of the first valve piece in the first channel, while blocking or unblocking of the communication between the inflow channel and the first channel via the second channel is controlled by movement of the second valve in the second channel. In this way, the valve enables opening or closing of the supply path through dual control by the first valve piece and the second valve piece.