The present invention has for its object to provide, in an environment where plural radio systems coexist, a feed forward amplifier capable of adaptively selecting a frequency band. The feed forward amplifier of the present invention comprises a distortion detection circuit and a distortion elimination circuit and has n first vector adjusters 4 which have different operating frequency bands and are inserted in a first vector adjustment path 14 of the distortion detection circuit; and n second vector adjusters 11 which have frequency bands corresponding to those of first vector adjusters 4 and are inserted in a second vector adjustment path 8 of the distortion elimination circuit. By means of a first switching means 3 selecting one first vector adjuster 4 and a second switching means 10 selecting a second vector adjuster 11, the frequency band for which distortion component is compensated in the feed forward amplifier is controlled by switching.