A bus wiring plate body (20), for an electric coupling box, is arranged in a manner that bus bar members (23, 24) are wired between pre-hardening epoxy resin plates (21, 22) and these pre-hardening epoxy resin plates are subjected to a heat pressing process to thereby integrate the pre-hardening epoxy resin plates (21, 22) and the bus bar members (23, 24) in a laminated state. When hardened epoxy resin plates (25, 26) are disposed outside of the pre- hardening epoxy resin plates (21, 22), respectively, the strength of the bus bar wiring plate body (20) can be improved. Thus, since the bus bar members (23, 24) are sealed in an insulated state, leak current is reduced. Further, the thickness of the bus bar wiring plate body (20) is reduced to a large extent, so that the electric coupling box can be miniaturized and lightweighted.