A lever 30 includes two arms (31), a coupling (32) coupling base ends (31R) of the arms (31) and an operating portion (33) coupling tips (31F) of the arms (31). The lever (30) is supported rotatably on a housing (10) with rotary shafts (34) formed on the coupling (32) serving as a fulcrum. Two sliders (40) are mounted in the housing (10) while being fit to drive shafts (38) of the lever (30) and slide in conjunction with the rotation of the lever (30). The sliders (40) are formed with cam grooves (43) configured so that cam followers (53) of a mating housing (51) slide in contact with the cam grooves (43) as the sliders (40) are slid.