A bend (14A) on an inner peripheral surface (15) on the inside of the bending direction of a bent portion (14) is formed as an arc. By forming the bend (14A) into an arc, the inner peripheral surface (15) on the inside of the bending direction of the bent portion (14) has a recess (16) formed thereon along the axis (13) direction as an example of a cross-section widening portion, where the cross-sectional area of the flow path of a pipe body (12) is widened.
