PURPOSE: To make a connection capable of the plug cap with an earth plug provided, by connecting a plug cap, to which the socket for the earth plug is constructed, to the wiring appliance without a socket for the earth plug.

CONSTITUTION: To a plug cap 1, electrically connected to an equipment, is installed an earth plug blade 3 in addition to plug blades connected to the power source. The construction of a wiring appliance 4 comprises an insulator unit 5, plug sockets 6 for insertion capable of the plug blade 2, an earth plug socket 7 capable of inserting the earth plug blade 3, plug blades 8, made in one unit with the plug socket 6 and capable of inserting into plug sockets 11 on the opposite wiring appliance 10, and a clip 9 electrically connected to the earth plug socket 7. Accordingly, in a use of this appliance 4, the plug cap 1, with the earth plug blade 3 provided, can be simply connected to the wiring appliance 10, capable of facilitating the work of earth connection.