Abstract: In a power supply changeover type amplifier arranged so that the voltages supplied from a plurality of power supplies to a power amplifying circuit are varied in accordance with the magnitude of level of an input signal which is to be amplified, arrangement is provided so that the plurality of power supplies having mutually equal output voltages are connected together in parallel and/or in series in accordance with the magnitude of the level of the input signal, and that the voltages resulting from the connection are supplied to the power amplifying circuit, to thereby enhance power efficiency of the amplifier and materialize its power supply section having a compact size and a light weight.