In the present study, the correlation between subjective assessment and EEG for essential odors were investigated quantitiatively. EEG signals were measured from 19 electrodes according to the International 10-20 system (Fp1, Fp2, F3/4, F7/8, Fz, C3/4, Cz, P3/4, Pz, T3/4, T5/5, O1/2) from 8 healthy males subjects for four odor (Rpse oil Bulgarian, Lemon oil misitano, Jasmin abs, Laverder oil france (KIMEX co.Ltd) conditions. The result of the subjective assessment shows the most pleasant odor for each subject, and the power spectrum of α/(α+β) of EEG signals form the most pleasant odor was compared with those form the control condition. Which has no odor at significantly at T4, T6 compared to the control condition. This result implies that the parameter. Power spectrum of α/(α+β). Could be an important index for signifying the levels levels of pleasantness for odors.