PURPOSE: To sterilize readily packed foods efficiently, quickly, uniformly, and securely, by transferring them from a sterilizing bath retaining hot water under pressure to a cooling water bath successively.

CONSTITUTION: The sterilizing bath 1 is charged with hot water from the hot water circulating device 5, compressed air is sent from the pipes 45, 49, and 411 so that the sterilizing bath 1 and the cooling bath 14 charged with cooling water are put under pressure. The feeding part 9 and the removing part 19 are separated from the sterilizing bath 1 and the cooling bath 14 by the plate 7 lifted by the air cylinder 81 through pressure difference. The basket 61 wherein packed foods are put is fed to the feeding part 9 at normal pressure, the valve 13 is handled to make the pressure of the feeding part 9 equal to that of the sterilizing bath 1, and the lifting plate 7 is lowered so that the basket 61 is sent to the sterilizing bath 1. The basket 61 is transferred to the cooling bath 14 by operating the air cylinders 81, 85, and 86, and lifted to the removing part 19 by the lifting plate 7', The pressure of the removing part 19 is returned to normal pressure by handling the valves 134 and 135 and the basket 61 is taken out. The valves 135 and 134 are handled to keep the removing part 19 at a given pressure and a series of operations is repeated.