When switching the mode of a power amplifier between compressed mode and uncompressed mode, accurate transmission power control is realized. A transmission power control method includes setting a power setting value of mode to switch to, such that an inter-mode output power error is canceled (equal to step ST21), calculating an intra-mode output power error from the power setting value of the mode to switch to (equal to step ST23), calculating a gain linearity value based on the power setting value of the mode to switch to and an output power error of the intra-mode (equal to step ST24), and resetting the power setting value of the mode to switch to based on the gain linearity value (equal to steps ST25 and 26).