The present invention discloses a cryogenic receiving amplifier using a gallium nitride high electron mobility transistor (GaN HEMT) as an amplifying device in a cryogenic temperature environment. The cryogenic receiving amplifier includes an input matching circuit which makes an impedance matching between a gate of the amplifying device and an outside of an input terminal, a gate biasing circuit which applies a DC voltage to the gate of the amplifying device, an output matching circuit which makes an impedance matching between a drain of the amplifying device and an outside of an output terminal, and a drain biasing circuit which applies a DC voltage to the drain of the amplifying device. The cooled temperature is preferably set to 150 K or below, and the GaN HEMT may be illuminated with light of a blue LED.