An ultralow-temperature low-noise amplification apparatus of high sensitivity which realizes a small size, a light weight, a low electric power consumption and a low price. As the insertion loss caused by high-frequency cables and a superconducting filter installed as a first signal transmitting device before a first-stage amplifier is most responsible for any increase in the noise figure of the ultralow-temperature low-noise amplification apparatus as a whole, they are formed from a material causing only a small insertion loss to reduce the noise figure of the apparatus effectively. A high-frequency cable forming a third signal transmitting device not affecting the noise figure of the apparatus substantially is formed from a material of low thermal conductivity, so that it is possible to prevent any external heat from entering a heat-insulating container through an output connector to hold the interior of the container steadily at a low temperature and thereby keep the noise figure of the apparatus at a low level.