PURPOSE: To lessen the capacity for enclosing an instrument of a control box so as to lessen the size thereof by arranging an insulating cover between a connection plug and a connection plug-socket and fixing the connection plug and the connection plug-socket through the insulating cover.

CONSTITUTION: In the case of separating an electric circuit by a wiring connector, an insulating cover 10 is inserted into a pin socket 7 of a connection plug- socket 5 which is fixed by engaging a hook 14 and a latched protrusion 9. A separated connection plug 4 is inserted into pin holes 11 of the insulating cover 10 and fixed by a hook 13 and a latched protrusion 8. While, in the case of removing the insulating cover 10, the connection plug 4 and the connection plug-socket 5 are connected to each other to remove the insulating cover 10, as already known. The wiring connectors are thus isolated each other through small capacity. Refuse is further prevented from being attached to a contact pin and the pin socket to hold the connection plug.