To obtain a reversing valve with a simple structure/consisting of a comparatively small number of simple manufacturing and assembly elements and the action of which is reliable and effective.

A valve member 24, in a first position, communicates a high pressure port to a second system port and also a low pressure port to a first system port. In a second position, the valve member communicates the high pressure port to the first system port and also the low pressure port to the second system port. As the valve member, in the first/second positions, obstructs the communication between the high pressure port and low pressure port and prevents the leakage between the high pressure port and low pressure port, in the first or second position, the valve member receives a net differential pressure acting so as to seat surely. An actuator 28 unseats the valve member to facilitate the movement to the other position and changes the direction of the net differential pressure acting to the valve member so as to move it away from the first or second position.