A Doherty amplifier (10) according to the present invention includes: a distribution unit (11) that distributes input signals; a main amplifier (12) that amplifies a first distributed signal output from the distribution unit (11); a transmission line unit (13) that transmits the first distributed signal amplified by the main amplifier (12); a peak amplifier (14) that amplifies a second distributed signal output from the distribution unit (11); a transmission line unit (15) that transmits the second distributed signal amplified by the peak amplifier (14); a synthesizing unit (16) that synthesizes the first distributed signal and the second distributed signal, and outputs a synthesized signal; and an impedance transformation unit (17) that performs an impedance transformation of the synthesized signal output from the synthesizing unit (16). The impedance transformation unit (17) includes a plurality of λ/4 transmission lines connected in series.