To provide a valve which is actuated regardless of fluid pressure by retaining to a position where a channel is opened when applying force exceeding deviation force for retaining movable means to a position to close the channel and the channel is closed by a bellows when applying force by pressurized fluid in a chamber.

A compression spring 34 closes a channel 20 by a valve sealing part 19 by applying upward force to a piston 26. Even though pressurized fluid is delivered to an inlet port 6, force to upwardly move a stem 24 by a contracted bellows 24 is equal to or little bit stronger than force applied to the valve sealing part 19 by pressurized fluid. Thus, fluid may not open the valve sealing part 19. When air pressure of the compression spring 34 that overcomes force applied to the piston 26 is applied from an opening 30 to the piston 26, the stem 24 is downwardly pushed so as to open the valve sealing part 19. Hereupon, fluid flows from the inlet port 6 to an outlet port 8. Therefore, this microvalve can be efficiently actuated regardless of fluid inlet pressure.