Abstract: A method for heat sterilizing an artificial kidney comprising a receptacle having accommodated therein permselective hollow filaments and including inlet and outlet ports for the blood and inlet and outlet ports for a dialyzate, which comprises(a) filling a primer consisting of water or a water solution into the artificial kidney,(b) connecting a pressure buffer tank to at least one of the inlet and outlet ports,(c) sealing the remaining ports by stopper means,(d) heating the artificial kidney to a temperature of 80.degree. to 130.degree. C. to heat sterilize it, and moving the gas and a part of the primer in the artificial kidney which have been expanded by heating to the pressure buffer tank,(e) cooling the artificial kidney to return the primer in the buffer tank to the artificial kidney, and(f) aseptically sealing the port connected to the pressure buffer tank; and artificial kidneys of specified constituent elements suitable for use in heat sterilization by this method.