The effects of gamma ray and electron beam irradiation on paper disinfection were evaluated. The paper was irradiated with 10-100 kGy gamma rays and electron beams which were higher than the recommended dose for paper disinfection. After irradiation, the mechanical properties and color of the paper and the cellulose chain scission rate were evaluated. In the case of paper strength, it decreased after 25 kGy irradiation, whereas the discoloration of paper appeared after 10 kGy irradiation. It cannot confirm the effect on paper only with changes in mechanical strength and color in the recommended range of 0.5-10 kGy for actual paper disinfection treatment. On the other hand, even with 10 kGy irradiation, the degree of polymerization of cellulose paper was reduced by ~50%. Cotton linter paper with a degree of polymerization of about 2,000 was predicted to decrease by about 7% after being irradiated with a 1 kGy gamma ray and electron beam. To evaluate the irradiation effect on paper, it is therefore more reasonable to evaluate the degree of polymerization rather than the strength and color of the paper.