To attract metal chips or the like contained in working fluid by an attracting member to separate them from the working fluid and prevent an orifice from being clogged with the metal chips or the like by providing an attracting member made of magnet on at least either of a housing and a rotor so as to contact with working fluid.

An attracting part 34b is for attracting minute metal chips and metal powder made of steel contained in working fluid, and the surface is formed with recessed parts 34c consisting of one parts of spherical faces. The recessed part 34c increases the surface area of the attracting part 34b so as to attract more metal chips or the like, and the an attracted metal chip or the like is prevented from breaking away from the attracting part 34b by the flow of working fluid. Further the recessed part 34c comprises a through hole penetrating the attracting member 34. Consequently, an orifice 20 can be prevented from being clogged with metal chips or the like.