PURPOSE: To prevent occurrence of water hammer so as to enable the prevention of noise or damage of piping, etc. and adjust the opening degree of a valve accurately and secure large flow by arranging the constitution such that the valve body contacts with or separate from a valve seat accompanying the contacting/separating action to the valve seat of a rotor attendant upon the rotation of a rotor.

CONSTITUTION: When a current is applied to a stator 24, a magnetic field is generated, and a rotor is rotated by the relation with the magnetic force of the rotor 16. Next, the rotor 16 ascends while rotating, resisting a spring 22, and the quantity of ascent can be controlled by the current application time to the stator 24. Moreover, the valve body also ascends accompanying the ascent of the rotor 16, so a valve seat 30 is released, and the fluid checked inside the valve chamber 36 flows out in the direction of an outlet 38 from the valve seat 30 by fluid pressure. Next, when the current application to the stator 24 is stopped, the fastening force to the spring 22 is released, and the spring 22 tries to return by accumulated energy. Accordingly, the rotor 16 descends, being rotated in the reverse direction to the time of ascent by the spring 16, and falls to the original position. As a result, the valve body 28 blockades the valve seat 30 again, and stops the flow of the fluid inside the valve chamber 36.