Various oral mucosal diseases such as oral potentially malignant disorders（OPMD）and squamous cell carcinoma （SCC）may develop in the oral cavity and are difficult to differentiate. Optical instruments are not invasive and can be repeatedly used. Since 2010, we have used optical instruments effectively to improve diagnosis and treatment. In this study, we conducted subjective and objective evaluations using optical instruments for distinguishing between leukoplakia and SCC. Eighty-two patients diagnosed with SCC and leukoplakia at the Department of Oral and Maxillofacial Surgery, Tokyo Dental College, between April 2017 and March 2018 were selected and evaluated using optical instruments. Also, an oral cancer screening model that used AI（AI oral cancer screening system：AIOS）was prepared and its effectiveness was evaluated. In the subjective evaluation by optical instruments, Fluorescence Visualization Loss（FVL）was confirmed in all SCC cases. In the objective evaluation, SCC was lower than leukoplakia in luminance（SCC 52.6 vs Leukoplakia 74.5cd/m2）. In the coefficient of variation of luminance, SCC was higher than leukoplakia in luminance（SCC 0.22 vs Leukoplakia 0.12）. Regarding luminance ratio, SCC was lower than leukoplakia in luminance（SCC 68.0 vs Leukoplakia 108.8％）. In the objective evaluation, statistical differences were found in luminance, standard deviation and coefficient of variation of luminance and luminance ratio. When AIOS was used to evaluate 20 new data, the correct diagnosis rate was 97.5％ after learning with 200 teacher data. It is suggested that subjective and objective evaluations using optical instruments may be useful for differentiating leukoplakia and SCC.