To make it easy to pull out a plug in a simple structure.

A cross-sectionally rectangular plug-in hole 11 which is a little larger than a cross-sectional face of a male contact piece of the plug is penetrated through housings 1, 2, and a female contact piece 8 to pinch the male contact piece of the plug is installed in the housings 1, 2. If the plug is inserted, the base side of the male contact piece of the plug is fitted into the plug-in hole 11, and the tip side of the male contact piece is pinched by the female contact piece 8. The plug-in hole 11 is not increased in the longitudinal length seen from the insertion direction of the plug, and both longitudinal side faces are tilted faces 12, 13 by being tilted from the insertion direction of the plug on the same side and on one side of the longitudinal direction. If the plug inserted into the plug-in hole is tilted in the same direction as the tilted faces 12, 13 of the insertion hole, the area where the male contact piece of the plug is pinched by the female contact piece 8 decreases, or the male contact piece of the plug is pulled out from the female contact piece 8.