A bidirectional converter (CONV1-CONVn) capable of supplying and regenerating an electric charge is disposed between a section where an input voltage is inputted and a section where an output voltage is outputted, an amplitude change monitoring circuit (10) detects the RF input signal envelope, and a converter switching circuit (11) controls the supplying and regeneration of the electric charge as performed by the bidirectional converter (CONV1-CONVn) so that the output voltage tracks the change in amplitude of the input signal. An output-capacitor capacitance estimation means (13) estimates the capacitance of an output capacitor (Co) from the voltage and electric current thereof. A delay time detection circuit (12) ascertains the delay time of a power supply device (111) for a high-frequency power amplification circuit and makes adjustments using a delay adjustment circuit (22). Thereby configured are a power supply device for a high-frequency power amplification circuit and a high-frequency power amplification circuit in which the power supply voltage for the high-frequency amplification circuit is changed tracking a high-frequency signal envelope.