PURPOSE: To smoothly flow oil, in case that a strainer is clogged through circulation of the oil in a first direction, in a second direction which is a reversed direction to the first direction.

CONSTITUTION: A strainer arranging chamber 1 is formed on an oil passage 5, while a strainer support member 2 is arranged inside the strainer arranging chamber 1 slidably in both pressurizing direction, that is, A direction and a pressure reducing direction. A first opening 3a is formed on the strainer arranging chamber 1 at its end face in the pressurizing direction, while a second opening 3b is formed on a certain position of an end face in the pressure reducing direction so as not to superpose on the first opening 3a, in both pressurizing and pressure reducing directions. A strainer 22 is installed on the strainer support member 2 in such a direction as to interrupt circulation of oil inside the strainer arranging chamber 1. A passing hole 2 is formed on a portion of the strainer support member 2 which is superposed on the second opening 3b in a sliding direction for circulating oil without passing the strainer 22.