An object of the present invention is to provide a novel method for detecting irradiation treatment of foods. The present invention provides a method for detecting irradiation treatment of foods comprising the steps of (A) obtaining a fraction containing one or more irradiation-generated fragments of natural high-molecular weight compound(s) from a food sample, and (B) reacting the fraction with one or more antibodies capable of recognizing the one or more fragments, thereby detecting the one or more fragments. The invention also provides a kit for detecting irradiation treatment of foods.