Oolong tea has an adequate amount of L-theanine acid, which can definitely affect human brain signal activity. Consequently, this study aimed to classify the effect level of L-theanine acid in Oolong tea relies on different participants focused on memorization and meditation state. An attention of the human brain was determined via electroencephalography (EEG) during the book reading state compared to not drinking and drinking conditions. To describe the memorization and meditation activity, this study focused on theta wave and alpha wave altogether. This properly measures a voltage fluctuation of these brain signals, as higher attention frequency indicated improving in mentioned state. Furthermore, Neural network performed the data classification of converted data in this study for high accuracy results. Each classified group was varied depending on the information of specified participants, i.e. gender, age, and body mass index (BMI). Obviously, several participants had a different effect level on L-theanine acid. Also, age, gender, and BMI of all participants were not totally affecting the effectiveness of L-theanine in this study. In conclusion, the results of this study represented that L-theanine in Oolong tea significantly affected the increasing of memorization and meditation. This result beneficially supports the production-proven of Oolong tea in the future apparently.