A radio transmission apparatus and a radio transmission method suppress lowering of the throughput caused by switching between the single carrier communication method and the multi-carrier communication method while suppressing increase in the signaling amount. A PHR threshold value setter sets a threshold value at a position greater by a predetermined value than the PHR at which the throughput performance of the SC-FDMA coincides with that of the OFDMA. A trigger signal transmission judger judges that a mobile station transmits a trigger signal for switching from the OFDMA to the SC-FDMA if the PHR in the OFDMA communication method is lower than the threshold value.