There is provided with an amplifier comprising: first and second power amplifiers; a first path configured to output first and second input signals to the first and second power amplifiers; a second path configured to divide a first input signal, output one of divided signals to the first power amplifier and output the other divided signal to the second power amplifier; a first path changeover unit configured to change over the first and second paths; a third path configured to output first and second power amplified signals from the first and second power amplifiers; a fourth path configured to combines a first power amplified signal through an impedance conversion unit from the first power amplifier and a second power amplified signal from the second power amplifier at a combining point and output a combined signal; and a second path changeover unit configured to changeover the third and fourth paths.