PURPOSE: To prevent the yellowing of a product by performing the γ-ray radiation sterilization of the vinyl chloride resin product under the existence of alcohol.

CONSTITUTION: A vinyl chloride resin product and alcohol are put in the packing material of a sealing system, and γ-rays are radiated from the outside of the sealing system. A medical apparatus requiring γ-ray radiation sterilization, e.g. a catheter, a blood bag, a tube, is referred as the vinyl chloride resin product. Ethanol is most suitable for the alcohol. The alcohol 0.3-2.0 pts.wt., preferably 0.5-1.0 pts.wt., is used against the vinyl chloride resin product 100 pts.wt. for γ-ray radiation sterilization. The yellowing of the product can be prevented.