Alcoholic beverages are a well-known risk factor for cancer. N2-Ethyl-2'-deoxyguanosine (N2-Et-dG) is a promising biomarker for alcohol-associated cancers. However, the lack of a convenient detection method for N2-Et-dG hinders the development of practical DNA damage markers. Herein, we develop a detection method for N2-Et-dG using a single-molecule quantum sequencing (SMQS) method and machine learning analysis. Our method succeeded in discriminating between N2-Et-dG and dG with an accuracy of 99%, using 20 signals. Our developed method quantified the mixing ratio of N2-Et-dG from a mixed solution of N2-Et-dG and dG. It is shown that our method has the potential to facilitate the development of DNA damage markers, and thus the early detection and prevention of cancers.