In solenoid valve provided with: a valve case that has an annular collar expanding in a radial direction of an opening, which is opened at an axial end surface, and accommodates a valve body inside; and an annular seal member mounted in an annular recessed groove provided on one axial end surface of the collar of the valve case, the collar includes a through-hole penetrating the collar in an axial direction, and a connecting portion connecting the through-hole and the annular recessed groove, the through-hole has a reduced diameter portion, and the seal member includes an annular portion mounted in the annular recessed groove and a protruding portion protruding at least in the axial direction with respect to the annular portion and penetrating the through-hole, the protruding portion including an enlarged diameter portion having an outer diameter φD1 (>φd2) larger than an inner diameter φd2 of the reduced diameter portion of the through-hole.