Provided are a method for the sterilization of powdery or granular substances which can protect powdery or granular substances from quality deterioration caused by heating and which can attain sufficient sterilization effect and a sterilization apparatus suitable for the method. A method for the sterilization of powdery or granular substances, characterized by comprising the heating/pressurizing step of feeding a powdery or granular substance into a heating gas flow pipe kept in a heated and pressurized condition and transferring the powdery or granular substance while bringing the powdery or granular substance into direct contact with a condensable heating gas for 0.008 to 2 seconds in the heating gas flow pipe and the instantaneous vacuum sterilization step of releasing the condensable heating gas and the powdery or granular substance instantaneously into a space having a pressure lower than that in the heating gas flow pipe to boil the water contained in microorganisms adhering to the powdery or granular substance and thus destroy the tissue of the microorganisms； and an apparatus for the sterilization of powdery or granular substances by the method.
