The invention provides a PLC transmission instrument which comprises an input circuit and a plurality of output circuits. The input circuit is used for being connected with a power supply. The output circuits are connected with the input circuit and are connected in parallel. Each output circuit comprises three output live lines and an output null line. A first indicating lamp is connected between each output live line and each output null line to indicate whether a corresponding output live line is electrified. The output lines are used for being connected with equipment to be detected. Each output circuit line is connected with a first switch in series. According to the technical scheme, the corresponding indicating lamp is connected between each live line and each null line to indicate whether a corresponding output live line is electrified, and the function of judging of phase loss of power supplying is achieved.