PURPOSE: To provide a supercritical helium generating device, capable of generating cryogenic supercritical helium efficiently and stably by a simple constitution for the device.

CONSTITUTION: Helium gas in a low-pressure side liquid helium reserving tank 32 is sucked by an ejector 40 to bring the inside of the reserving tank 32 into a condition of low pressure. The driving fluid of the ejector 40 is cooled by heat exchangers 33, 34 in liquid helium reserving tanks 31, 32 to supercritical helium and is introduced into a high-pressure side liquid helium reserving tank through the ejector 40. The liquid helium of the low-pressure side liquid helium tank 32 is supplied while expanding high-pressure and low-temperature helium, deprived by cooling through the first heat exchanger 33 in the high-pressure side liquid helium reserving tank 31, through, a JT value 42.