A bit-power distribution ratio calculation unit measures several times an SNR of periodic noise occurring on a communication line to calculate several times, according to the measurement results of the SNR thus measured, a bit distribution ratio to be assigned to each carrier for data transmission for each measurement result. The calculation unit compares the calculated bit distribution ratios with each other to detect a minimum bit value of each carrier to calculate, according to the detected minimum bit values of the respective carriers, a minimum bit distribution ratio including the minimum bit value of each carrier. The calculation unit delivers the minimum bit distribution ratio to a demapping unit and a mapping unit, which conduct data transmission using the minimum bit distribution ratio. Therefore, a multicarrier transmission device can efficiently conduct multicarrier transmission even at occurrence of non-periodic noise.