A pressure introduction hole of a case has a first introduction hole extended in a predetermined direction to define a first end opening and a second introduction hole extended in a direction different from the predetermined direction to define a second end opening opposite from the first end opening. The second introduction hole is communicated to the first introduction hole. An angle defined between a wall surface of the first introduction hole and located adjacent to the second end opening and a wall surface of the second introduction hole and connected to the wall surface of the first introduction hole is larger than or equal to 90°. The second introduction hole has a communication part communicating with the first introduction hole, and a space increasing chamber further extending from the communication part away from the second end opening.