Organophosphorus pesticides such as glyphosate and glufosinate are used worldwide, and environmental regulatory values are being adopted in many countries due to their potential toxicity. In the present work, a pretreatment-free analytical method is established in which these two compounds with their metabolites are isolated fromeach other by anion-exchange HPLC using ammonium acetate (70mM, pH 3.7) as eluent, and theyaredetected by triple quadrupole ICP-MS. Very low detection limits of 0.03-0.17μg L-1 are acquired through the detection of P+ as PO+ via oxygen reaction mode, and quantitative recovery was obtained from the spike-recovery test on river water samples containing phosphate ion as an isobaric interferent. In addition, a constant sensitivity per molar concentration was achieved regardless of the compounds due to the powerful ion source of ICP-MS. This property suggests that semi-quantitative analysis of unknown P-bearing compounds is possible from one calibration curve.