A pair of first leg portions of a retainer have first taper surfaces at distal end sides on surfaces on the side to which a first pipe is to be inserted. The first taper surfaces cause the retainer to move from an initial position to an insertion position by an axial-direction pressing force from an annular protrusion, during a period until the first pipe is inserted to a regular position. During the period until the first pipe is inserted to the regular position, a pair of second leg portions restrict the retainer from moving from the initial position to a confirmation position. In a state in which the first pipe is inserted to the regular position, the pair of second leg portions allow the retainer to move from the initial position to the confirmation position.