The oxide layer of atomized U-Mo particle nuclear fuel was analyzed using the electron probe microanalyzer (EPMA) wavelength dispersive spectroscopy (WDS) image mapping function. The density of the used nuclear fuel was 2.6 gU/cm3 and the burnup was 16.4%. Typically, measurements of the oxide layer of most nuclear fuel specimens that have been irradiated for research and experimental purposes in the Korea Atomic Energy Research Institute HANARO research reactor have been performed using metallographic equipment. But an oxide layer was not observed in the nuclear fuel used in this study. Therefore, we conducted this study to confirm the presence and thickness of the oxide layer using EPMA WDS image mapping analysis. We were able to confirm the existence of the oxide layer, but there were many shortcomings in determining the exact thickness of the oxide layer using only the identified X-ray image mapping. In this paper, we present a way to accurately measure the oxide layer by recalling the derived original X-ray values as Excel data. To accurately analyze the oxide layer derived from the image, a preliminary study was performed using samples taken from an irradiated Zr-2.5Nb pressure tube from a CANDU pressurized heavy water reactor. In the preliminary study, the exact thickness of the oxide layer measured by metallography and the results obtained by measuring the thickness of the oxide layer with Excel data obtained by X-ray mapping were compared, inferred, and applied to this study. In this study, a method of accurately measuring the thickness of an oxide layer using Excel data obtained by EPMA WDS image mapping of the oxide layer of plate-type fuel, which was not confirmed using metallography equipment, is described in detail.