The invention provides a linearizer. Thus, cost and inserting loss can be reduced, and yield can be increased. The linearizer includes: a branch circuit (1) having an input transmission line (1a) connected between an input terminal (IN) and a branch point, a first output transmission line (1b, 1c) connected between the branch point and a first output terminal (OUT1), and a second output transmission line (1c) connected between the branch point and a second output terminal (OUT2); a diode (2) having an anode connected to the branch point and a cathode; and a bias circuit (3) biasing the diode (2).