Disclosed herein is an amplifier circuit having improved linearity and frequency band using a MGTR. The amplifier circuit comprises an amplification unit including a main transistor and an auxiliary transistor, an attenuation unit including inductors respectively connected to the source of the main transistor and the source of the auxiliary transistor, a capacitor connected at one end thereof to the sources of the main transistor and auxiliary transistor and connected at the other end thereof to the gates of the main transistor and auxiliary transistor, and an output unit connected to the drains of the main transistor and auxiliary transistor.