Parts of a first coupling and a second coupling that protrude from manifold blocks each have the shape of an elongated tube. When the first coupling and the second coupling are viewed in the axial direction, the traverse direction of the first coupling and the second coupling agree with the arrangement direction of manifold blocks. A part of the tube insertion hole is a small diameter hole, which is a stadium-shaped hole. When the first coupling and the second coupling are viewed in the axial direction, the traverse direction of the small diameter hole agrees with the traverse direction of the first coupling and the second coupling.