PROBLEM TO BE SOLVED: To provide both an apparatus for air blowing change, with which in a treatment tank of a retort sterilizer or sterilizing machine, a gas flow channel for drying and cooling can be changed, an air stream is uniformly circulated and neither insufficient drying or nor deficient cooling occurs and a method therefor. SOLUTION: This apparatus for air blowing change during drying and cooling in a retort sterilizer, etc., has a structure in which guide blade groups 4 which are pivotally supported each rotatably in the horizontal direction at both right and left sides of trays 3 storing materials to be treated in the treatment tank 1 of a retort sterilizer or sterilizing machine and rotated and connected by a driving source 8 outside the tank are arranged, guide blades at the uppermost parts 4a or the lowermost parts 4b among the guide blade groups 4 are brought into contact with the inner wall of the treatment tank 1 to close the flow channel, on the contrary, guide blades at the lowermost parts 4b or the uppermost parts 4a are opened, the intermediate guide blade groups 4 are successively piled up on end parts of continuously adjacent guide blades so as to open or close the flow channel and the flow channel of a gas introduced from a gas inlet 12 and outlet 13 of the treatment tank 1 is changed by the guide blade groups 4.
