To provide a power line carrier communication apparatus which reduces the transmission power without costing, and saves the power consumption in waiting for reception.

The apparatus has a detecting means for detecting the receiving level of superposed received signals and a transmitting means for variably controlling the transmitting level of transmitted signals superposed on power lines. The apparatus sets the transmission level of the transmission means, based on the receiving level detected by the level detecting means or sets a frame system for transmitting/receiving signals at fixed time intervals, which opens a time slot for catching a frame for a prescribed time period, to turn on a circuit for processing received signals for a prescribed time period with a timing for synchronizing with frames.