A Doherty amplifier comprising: a first main amplification element to amplify a first signal; a second main amplification element to amplify the first signal amplified by the first main amplification element; a first auxiliary amplification element to amplify a second signal; a second auxiliary amplification element to amplify the second signal amplified by the first auxiliary amplification element; a combination circuit to combine the first signal amplified by the second main amplification element and the second signal amplified by the second auxiliary amplification element; and a phase adjustment circuit connected between the first auxiliary amplification element and the second auxiliary amplification element, is wherein the phase adjustment circuit configured to adjust either a phase of a return signal going to the first auxiliary amplification element as a result of passage of the first signal amplified by the second main amplification element through the second auxiliary amplification element as the return signal, or a phase of the return signal going to the second auxiliary amplification element as a result of reflection of the return signal by the first auxiliary amplification element, at a time of a backoff operation of the second auxiliary amplification element, in such a way that a sum of the phase of the return signal going to the first auxiliary amplification element and the phase of the return signal going to the second auxiliary amplification element is not equal to 0 degrees in an operating frequency band of the first signal, wherein the phase adjustment circuit has a characteristic impedance of the same value as an output impedance of the first auxiliary amplification element at a time of a saturated operation or an input impedance of the second auxiliary amplification element at a time of the saturated operation, and wherein the time of the saturated operation is an operation when an output power of the first auxiliary amplification element is the same as an output power of the first main amplification element or an operation when an output power of the second auxiliary amplification element is the same as an output power of the second main amplification element. a first main amplification element to amplify a first signal; a second main amplification element to amplify the first signal amplified by the first main amplification element; a first auxiliary amplification element to amplify a second signal; a second auxiliary amplification element to amplify the second signal amplified by the first auxiliary amplification element; a combination circuit to combine the first signal amplified by the second main amplification element and the second signal amplified by the second auxiliary amplification element; and a phase adjustment circuit connected between the first auxiliary amplification element and the second auxiliary amplification element, is wherein the phase adjustment circuit configured to adjust either a phase of a return signal going to the first auxiliary amplification element as a result of passage of the first signal amplified by the second main amplification element through the second auxiliary amplification element as the return signal, or a phase of the return signal going to the second auxiliary amplification element as a result of reflection of the return signal by the first auxiliary amplification element, at a time of a backoff operation of the second auxiliary amplification element, in such a way that a sum of the phase of the return signal going to the first auxiliary amplification element and the phase of the return signal going to the second auxiliary amplification element is not equal to 0 degrees in an operating frequency band of the first signal, wherein the phase adjustment circuit has a characteristic impedance of the same value as an output impedance of the first auxiliary amplification element at a time of a saturated operation or an input impedance of the second auxiliary amplification element at a time of the saturated operation, and wherein the time of the saturated operation is an operation when an output power of the first auxiliary amplification element is the same as an output power of the first main amplification element or an operation when an output power of the second auxiliary amplification element is the same as an output power of the second main amplification element.