To provide a miniaturizable valve device for opening/closing a passage with structure not connecting an actuator to one axial end of a valve stem.

This valve device for opening/closing the passage is provided with a valve tube 3 provided with a valve hole 4 and a valve seat 5, and a valve element 12. The valve element 12 is fixed, while the valve tube 3 is made movable to the valve element 12, and the valve tube 3 is moved to bring the valve seat 5 of the valve tube 3 into contact with the valve element 12 to close the valve hole 4, thus cutting off communication between the passage A and the passage B. The valve seat 5 of the valve tube 3 is separated from the valve element 5 to open the valve hole 4, thus communicating the passage A with the passage B.