Provided is a multi-carrier communication apparatus, power line communication circuit, and multi-carrier communication method capable of decreasing omission of carrier detection even when a plurality of communication apparatuses are simultaneously transmitting signals at the state of time discord. Digital signals transmitted from a digital signal-processing unit 1 are converted into analog signals by an analog circuit unit 2 and then transmitted from a pair of lines 61 and 62 via a communication transformer 3. The digital signal-processing unit 1 has a frequency carrier detecting unit 10 which detects the existence of a carrier on the basis of a frequency characteristic of the received signal and the frequency carrier detecting unit 10 detects the carrier by taking correlation between sub-carriers adjacent to each other at every other interval.