Background : Brain waves are generated by the neurons in the brain. Many scientists fixed the electrodes of the electroencephalogram (EEG) on the scalp to record the signal expression of continuous cerebral activity. EEG is widely used in clinical diagnosis. It can be used to screen epilepsy, depression, ementia, stroke, encephalitis, ADHD and other brain diseases. Also, many local and foreign studies on aromatherapy focused on the discussion of human skin absorbing essential oils. This study discusses the level of relaxation efficacy of inhaled essential oils via the human olfactory organs. Thus, this study intended to observe the effects of essential oil of Aucklandiae Radix and Cyperi Rhizoma on EEG activity. Methods and Results : We evaluated the effects of essential oil of Aucklandiae Radix and Cyperi Rhizoma, on human EEG activity. For this purpose, essential oil was extracted from Aucklandiae Radix and Cyperi Rhizoma by the supercritical extraction method. The effect of its inhalation on EEG activity was evaluated by measuring the EEG power spectrum in 20 healthy participants. EEGs signals were recorded using QEEG-8 system (LAXTHA Inc., Daejeon, Korea) from 8 grounding electrodes. The subjects were instructed to sit quietly, close their eyes and to breathe normally during the measurement. The fragrance stimulus was dipped in a paper (14 ㎝2) then placed about 3 cm in front of the subject's nose. EEG was recorded before and during the fragrance exposure for 30 seconds. The mean power values (μV) calculated for fast fourier transform (FFT) analysis indicators. The results were as essential oils of Aucklandiae Radix and Cyperi Rhizoma decreased the overall brain relative theta (θ waves), but increased relative beta (β waves), absolute gamma (γ waves), spectral edge frequency (SEF) and spectral edge frequency 95% (SEF95). Conclusion : The changes in the EEG activities following inhalation of Aucklandiae Radix and Cyperi Rhizoma suggest that the oil can improve psychological well-being by increasing attention and relaxation.