The concentrations of sulfur substances in fuel oil, which greatly contribute to air pollution and acid rain, are regulated by law in many countries, and these regulations are becoming stricter with the growing concern about their impact on the environment and the consequences for society. Here, using the easy-to-operate EDX-720 energy dispersive X-ray fluorescence spectrometer, we determined the limit of detection and limit of quantitation of sulfur. The energy dispersive X-ray fluorescence spectrometer can be used for simultaneous multi-element analysis of the elements from Na (atomic no. 11) to U (atomic no. 92). Next, we conducted simultaneous analysis of the elements in Conostan? S-21, a commercially-available oil standard, and determined the limit of detection for each element detected.