People are stressed out as society grows. According to the Comprehensive Survey of Living Conditions(2016), 47.7 percent of people are stressed. We live in today a stress society as the survey suggests. The researches of stress often employ NIRS to observe effects on the brain activity, but it has not been studied how stress can be reduced with aroma fragrances although they must have some effects on brain activity. In this study, we investigate how stress can be reduced by aroma fragrances by examining signals collected from the frontal cortex of subjects using NIRS. We ask twenty participants (male: 5 female:5) to do a quiet task operation (UK test). We do rest-tasking-aromatherapy experiments comparing them. Aroma fragrances are lavender, orange sweet peppermint and lemon