Among the different treatment processes, advanced oxidation processes have been drawing attention for decomposition of antibiotics in water and wastewater. The purpose of this study was to investigate and compare the degradation and mineralization of sulfamethoxazole and chlortetracycline by advanced oxidation processes such as ozone, UV, and gamma ray. Based on a 50% degradation efficiency, sulfamethoxazole (30 mg/L) required 25 min, 5 min, and 0.6 kGy, and chlortetracycline (30 mg/L) required 90 min, 5 min, and 0.3 kGy for ozone, UV, and gamma ray, respectively, indicating gamma ray is the most effective process for the degradation of antibiotics among the three advanced oxidation processes.