The combined electrolysis and catalytic exchange process has been selected for the water detritiation system for the ITER. In the front-end process of tritiated water electrolyzer composed of a solid polymer electrode, ion exchange resin beds are installed for processing effluent ions in the enriched tritiated water from the catalytic exchange column to avoid the deterioration of the solid polymer electrode. The tritium concentration in the circulation resin bed is evaluated to reach 1.09x1015Bq/m3. It is thus important to note the radiation-induced degradation in ion exchange resins. We studied the degradation effects in Amberlite[registered] and Diaion[registered] organic ion exchange resins caused by the irradiation with electron beam up to the integrated dose of 1500kGy. The procedures D2187-94 of the American Society for Testing and Materials were adopted for the evaluation of the water retention capacity, the backwashed and settled density, the salt splitting capacity, and the total exchange capacity of particulate ion exchange resins. A 20% decrease of total exchange capacity of the cation exchange resin, when irradiated up to 1500 kGy at room temperature, has been observed.