Provided is an amplifier including: a first transistor connected to a signal input terminal; a second transistor connected to a signal output terminal; a wiring line configured to connect the first transistor and the second transistor to each other; and a variable inductor circuit which is electrically connected to the wiring line, and is grounded via a capacitor for DC current interruption, wherein the inductance value of the variable inductor circuit is set to an inductance value for canceling a parasitic capacitance between the first transistor and the second transistor.