A power amplifier comprising: m (m is a positive integer equal to or greater than 2) sets that each comprises: a first amplifying unit and a second amplifying unit that each comprises a plurality of amplifying circuits (33, 35) connected in parallel wherein a bias voltage is adjustable in accordance with a control signal supplied from outside, amplifies an input signal by the plurality of amplifying circuits (33, 35), combines the amplified signals, and outputs the combined signal, wherein the first and the second amplifying unit (22, 23) each further comprise: a variable attenuator that attenuates an input signal in accordance with a control signal supplied from outside; and a variable phase shifter that delays a phase of an input signal in accordance with a control signal supplied from outside; a divider that divides an input signal to the first amplifying unit and the second amplifying unit; and a combiner that combines an output signal of the first amplifying unit and an output signal of the second amplifying unit and outputs the combined signal; an m divider that divides an input signal to each of m sets; and an m combiner that combines output signals of the m sets of the first amplifying unit and the second amplifying unit and outputs the combined signal. m (m is a positive integer equal to or greater than 2) sets that each comprises: a first amplifying unit and a second amplifying unit that each comprises a plurality of amplifying circuits (33, 35) connected in parallel wherein a bias voltage is adjustable in accordance with a control signal supplied from outside, amplifies an input signal by the plurality of amplifying circuits (33, 35), combines the amplified signals, and outputs the combined signal, wherein the first and the second amplifying unit (22, 23) each further comprise: a variable attenuator that attenuates an input signal in accordance with a control signal supplied from outside; and a variable phase shifter that delays a phase of an input signal in accordance with a control signal supplied from outside; a first amplifying unit and a second amplifying unit that each comprises a plurality of amplifying circuits (33, 35) connected in parallel wherein a bias voltage is adjustable in accordance with a control signal supplied from outside, amplifies an input signal by the plurality of amplifying circuits (33, 35), combines the amplified signals, and outputs the combined signal, wherein the first and the second amplifying unit (22, 23) each further comprise: a variable attenuator that attenuates an input signal in accordance with a control signal supplied from outside; and a variable phase shifter that delays a phase of an input signal in accordance with a control signal supplied from outside; a variable attenuator that attenuates an input signal in accordance with a control signal supplied from outside; and a variable phase shifter that delays a phase of an input signal in accordance with a control signal supplied from outside; a divider that divides an input signal to the first amplifying unit and the second amplifying unit; and a combiner that combines an output signal of the first amplifying unit and an output signal of the second amplifying unit and outputs the combined signal; an m divider that divides an input signal to each of m sets; and an m combiner that combines output signals of the m sets of the first amplifying unit and the second amplifying unit and outputs the combined signal.