In a side plate (52) of a retainer (50), a jig insertion groove (70) is cut at an upper end portion of its front edge. A releasing jig (J) is insertable into a gap between the bottom surface of the jig insertion groove (70) and a vertical front edge of a recessed surface (27) of a female housing (20). If the releasing jig (J) is rotated so as to be pried, the retainer (50) is pushed back diagonally downward along a guide groove (60) and reaches a temporary retaining position.