A power line transmission apparatus is not interfered by the noise of the public power for transmitting high quality video/audio signal. The power line transmission apparatus includes an isolating unit connected between an external power line and an internal power line for isolating a high frequency noise signal carried on the external power line and transmitting a first power signal of the external power line from the external power line to the internal power line, and a power line network interface. The power line network interface includes at least one digital signal input/output interface for inputting or outputting a digital signal, converting the digital signal, and modulating the converted signal into the first power signal to form a second power signal and transmit the second power signal to the internal power line. A home network system without noise signal interference is built by utilizing several power line transmission apparatuses.