PURPOSE: To miniaturize the above device and reduce the cost thereof by providing a poppet which opens and closes a poppet chamber at the poppet chamber facing a main oil passage of a valve body, and making the poppet pressure act on the back side of a plunger provided at the plunger chamber of a bypass oil passage.

CONSTITUTION: A poppet 36 which opens and closes a main oil passage 34 is provided at a poppet chamber 35 facing the main oil passage 34 of a valve body 31, and a plunger 42 is provided at a plunger chamber 41 facing a bypass oil passage 40 to open and close the bypass oil passage 40. Besides, a central oil passage 27 is provided at the plunger 42 to make pressure of the poppet chamber 35 act on the back side of the plunger 42, a spring 35 is provided inside the plunger 42, and a pilot fluid passage 43 leading to the plunger chamber 41 is provided. It is thus possible to build the poppet 36 and plunger 42 in the valve body 31 to manufacture a small-sized and inexpensive unit.