To effectively reduce oxygen concentration at a head space produced in a packing body, and prevent deterioration of oxygenic absorption ability of the packing body after sterilization.

In a sterilizing method for the packing body which consists of oxygen absorbable laminated materials having oxygenic absorption layer and has contents housed therein, the packing body is sterilized by relatively shifting the head space inside the packing body while a retort kettle is rotated.