PURPOSE: To prevent erroneous insertion and make it possible to mount connectors highly densely by forming an open part and a recessed part in a connector installation panel able to slide, and forming an extruded part corresponding to the recessed part in a connector hood for a cable.

CONSTITUTION: An I/O connector 5 and a connector 2 for cable connection are connected by inserting a connector hood 1 for a cable into an open part 8. After the connection of the connectors 2 and 5, an extruded part 3 is located in the back side of a panel 7. When the panel 7 is slid, the extruded part 3 and the panel 7 overlap to contact each other while differing from the positions of a recessed part 4 and the extruded part 3, so that the hood 1 is prevented from pulling out. That is, the extruded part 3 prevents error insertion and also the connector from pulling out. Error insertion of a plurality of the same connectors is prevented by altering the positions of the extruded part 3 and the recessed part 4 for each connector. Moreover, since the space for fastening a screw becomes unnecessary, highly dense mounting of connectors becomes possible.