PURPOSE:To obtain a high seed amplifier with high S/N configuration, small size and ease of handling by providing components constituting the refrigerating cycle and a motor driving the refrigerating cycle to the inside of a chassis of the amplifier employing a superconductive element. CONSTITUTION:An evaporator 4 for cooling a superconductive element and a condenser 5 implementing the refrigerating cycle together with the evaporator 4 are provided to the inside of the console 7 for the amplifier employing the superconductive element. Moreover, an expansion valve 6, a compressor 2 and a compressor driving motor 3 for the refrigerating cycle are provided. Then the superconductive elements used in the amplifier are all mounted in a unit 1 and in thermal contact with the evaporator 4. In starting the amplifier, the compressor driving motor 3 and a fan motor 10 are started and the cooling of the superconductive element unit is started by the evaporator 4. Then the superconductive element unit is cooled to the transition temperature of the superconductive element or below, the superconductive elements can be used by a signal from the internal temperature sensor to a controller 8.