A power amplifier includes a distributor distributing an input first signal to a second signal and a third signal delayed by about 2 phi degrees (45< phi <90) from the second signal, a first amplifieramplifying the second signal and outputting a fourth signal when a first-signal power level is not lower than a first level, a second amplifier amplifying the third signal and outputting a fifth signal when the first-signal power level is not lower than a second level that is greater than the first level, a first phase shifter receiving the fourth signal and outputting a sixth signal delayed by about phi degrees from the fourth signal, a second phase shifter receiving the fifth signal and outputting a seventh signal advanced by about phi degrees from the fifth signal, and a combiner combiningthe sixth and seventh signals and outputting an amplified signal of the first signal.