Effect of ${gamma}$-irradiation to cereal processed by-products was examined for antioxidative ability. Rice hull (RH), rice bran (RB) and barley bran (BB) were irradiated with 5, 10, 15 and 20 kGy of ${gamma}$-ray at 4.2 kGy/h. The amount of total phenol compounds of unirradiated RH, RB, and BB were 0.873 mM, 0.643 mM, and 0.377 mM, respectively. Irradiation up to 20 kGy did not show noticeable effect to the amount of total phenol compounds in RH, RB and BB. Electron donating abilities of RH, RB and BB were very similar, and they were not affected by irradiation. According to TBARS analyses, the inhibition abilities of lipid peroxidation of RH and RB were not affected by ${gamma}$-irradiation, while those of BB were decreased with irradiation. These results indicate that BB is more sensitive to ${gamma}$-irradiation than other rice processed by-products.