In an apparatus for connecting two generators to run in parallel, having plugs connectable to each generator output socket, an output socket connected to an electrical load, conductive paths that connect the plugs to the output socket while merging to a common path at a junction before the output socket, and a switching circuit that opens/closes the conductive paths, there are equipped with a connecting path that interconnects the conductive paths before the junction, a dummy load installed at the connecting path and current sensors installed at each conductive path. Disconnection of the plug from the socket is detected from the detected currents and the conductive paths are opened not to connect the generators to the electrical load, thereby preventing an output of the other of the generators from appearing at the terminals of the disconnected plug, and further preventing misjudging current change of the instantaneous no load condition as plug disconnection.