A power amplifier system includes a first power amplifier, a second harmonic generator, a phase shifter, and first and second adders. The first power amplifier amplifies a primary input signal. The second harmonic generator outputs a second harmonic by using a split part (signal) of the primary input signal as an input. The phase shifter adjusts a phase of the second harmonic. The first adder sums together a split signal of the primary input signal and an output of the phase shifter, thereby to produce an output. The second power amplifier uses the output of the first adder as an input. The second adder sums together an output of the first amplifier and an output of the second power amplifier, thereby to produce an output.