In a ground plate (110), the back of a conductive plate and the peripheral end portions of the surface are insulated (120) in advance. A plurality of L- or T-shaped tab terminals (100) are soldered to the ground plate (110). A connection terminal (140) to be connected with an electronic device is connected to one end portion of a wiring line (130), and a plug-in type connection terminal (150) to be connected with each of a plurality of projection terminal is connected to the other end portion. At the assembly, the tab terminal (100) is fitted in the plug-in type connection terminal (140) of the connection line, and this ground plate (110) is placed on the floor of a building to connect the connection terminal (140) of the connection line with the electronic device. This facilitates the assembly.