Chronic pain and related mental fatigue are responsible for degraded QOL of patients. Pain control based on Complementally and Alternative medicine (CAM) without drugs is promising for such people having various medical restrictions. A method using essential oils is a prime candidate for such CAM, however, its fundamentals are poor due to lack of physiological or neurological evidences. In this study, we systematically investigate effects of essential oils on brain activity based on Clinical Assessment for Attention and consider individual difference of pain sensations.