PURPOSE: To availably recover the heat being held by steel billet during cooling thereof, in cooling the high temp. steel billet, by a method wherein the high temp. billet is cooled in boiled water and the generated steam is converted to super-heated steam by the high temp. billet prior to cooling.

CONSTITUTION: High temp. steel billets B are supplied into plural ducts D while thrown into boiled water 3 in a boiled water tank 2 to be cooled to 100°C and the cooled billet is transferred through the tank 2 by a transfer means 7 to be taken out from an outtake port 6. Because the boiled water 3 is heated by the billets B to generate a large amount of steam, this steam is passed through the ducts D as high temp. steam 5 shielded from the air by a shield plate 4 to be heated by the radiant heat of the high temp. billets B prior to cooling transferred through the ducts D and the heat held by the billets is recovered as super- heated steam.