To provide an envelope tracking type amplifier that has high efficiency and small fluctuations, an output unit supplies an output signal that is adjusted corresponding to an input signal to a power supply terminal of the amplifier. The output unit includes an analog amplifying circuit that amplifies the input signal; a digital circuit that selectively outputs a first voltage or a second voltage that is lower than the first voltage; and first and second output circuits. The first output circuit includes a first integrating circuit that integrates an output signal of the digital circuit; and a combining section that combines an output signal of the first integrating circuit and an output signal of the analog amplifying circuit and outputs the combined signal to a power supply terminal of the amplifier. The second output circuit includes a second integrating circuit that integrates the output signal of the digital circuit; a resistor having two ends, one end being connected to an output terminal of the second integrating circuit, the other end being connected to an output terminal of the analog amplifying circuit; and a load connected to the output terminal of the second integrating circuit. The digital circuit outputs the first voltage where a voltage applied at the one end of the resistor is lower than the voltage applied at the other end of the resistor and the digital circuit outputs the second voltage when the voltage applied at the one end of the resistor is higher than the voltage applied at the other end of the resistor.