A groove is provided at an outer side of an outer wall of a pressure sensor in a radial direction, and opens at one end side in an axial direction of the pressure sensor. A horizontally extending stopper is provided at an inner wall of a sensor accommodation recessed portion. A fixing portion is provided on the outer side of the outer wall of the pressure sensor in the radial direction, and enters the stopper. The fixing portion protrudes outward in the radial direction from the outer wall of the pressure sensor accommodated in the accommodation recessed portion, and contacts the stopper in the axial direction.