To uniformly collect foreign matters of various sizes over the whole filter medium.

A required number of projected pressing parts 46 projected toward a housing part 26 for housing a filter medium 30 are formed on the inner wall surface of a case body 20 provided with an inlet hole 22 and an exhaust hole 24 for fluid opened therein. By pressing each pressing part 46 onto the filter medium 30 housed in the housing part 26 for compressing it, a compression part 32 having high collection efficiency of foreign matters mixed into the fluid is arbitrarily formed in the filter medium 30. Thereby, the foreign matters having various sizes are uniformly collected over the whole filter medium 30. The compression degree of the compression part 32 can be changed corresponding to the projecting amount of the projection part 46, and the collection efficiency of foreign matters is increased as the compression degree of the compression part 32 becomes larger.