An amplifying device includes a radio frequency (RF) signal input terminal to which an RF signal is input, a buffer circuit, a linearizer including a transistor, a power amplifier, and a control circuit. The control circuit outputs a first gate voltage when a level of the RF signal input is a first level, the first gate voltage causing the transistor to perform a class B operation. The control circuit outputs a second gate voltage when the level of the RF signal is a second level higher than the first level, the second gate voltage causing the transistor to perform a class AB operation. Output impedance of the buffer circuit that is seen from an input side of the linearizer is set such that a reflection loss of the RF signal input from the buffer circuit to the linearizer is a predetermined level or less.