PROBLEM TO BE SOLVED: To broaden resonance by a simple structure using an existing orifice passage.SOLUTION: The orifice passage formed at a partitioning member is formed of an annular groove 17, and a plurality of streamline change protrusions 20 which are formed into substantially-triangle shapes and whose apexes 21 are protruded toward mating sides are alternately arranged at an external peripheral wall 16a and an internal peripheral wall 16b which oppose the annular groove 17. By this arrangement, streamlines A, B are bent in zigzag between the streamline change protrusions 20, a large disturbance flow covering the whole of a flowing operating fluid is generated, large passage resistance is generated, a resonance frequency of liquid-column resonance is changed, and thus the broadening is achieved.