In a wide-range low-noise amplifier: an input terminal is connected to a base terminal of a first transistor, one end of a first passive element, and one end of a third passive element; an emitter terminal of the first transistor is grounded; a collector terminal of the first transistor is connected an output terminal, a base terminal of the second transistor, one end of a capacitance element, and one end of a second passive element; the other end of the first passive element is connected to the other end of the capacitance element; an emitter terminal of the second transistor is connected to the other end of the third passive element; and a power terminal is connected to a collector terminal of the second transistor and the other end of the second passive element. The amplifier decides an impedance of the third passive element in accordance with an impedance of the first transistor whose emitter size has been decided so as to be appropriate for a desired saturation level of the amplifier, thereby adjusting the input impedance.