Abstract: Connection and disconnection between an apparatus and an electric wire are made by fitting an electric wire side housing in an apparatus side housing inside a mounting hole or removing the electric wire side housing from the apparatus side housing, so that the need for time-consuming work for tightening or loosening a bolt or work for attaching a cover to a terminal block or detaching the cover from the terminal block as is conventional is eliminated and workability is good. In addition, the apparatus side housing can be fixed into the mounting hole by a stopper and a retainer, so that workability is good as compared with the case of fixing the apparatus side housing by bolt tightening.