This study investigated the effects of Lavandula angustifolia (L. angustifolia) aroma on the brain electrical activity evaluated by electroencephalogram (EEG) in female adults with sleep disorders. The subjects were 28 healthy female adults and their sleep disorders were classified by the Pittsburgh Sleep Quality Index. EEG electrodes were attached at the frontal (F3, F4), temporal (T3, T4), occipital (O1, O2), parietal (P3, P4), reference, and ground regions according to the International 10-20 system. Subjects were exposed to the L. angustifolia aroma for 3 min. Results showed that L. angustifolia aroma decreased the occipital and parietal alpha powers, and increased the frontal theta power and occipital beta power in subjects with good sleep quality. On the other hand, L. angustifolia aroma increased the theta power in the all cranial regions after aroma treatment in subjects with poor sleep quality. In conclusion, L. angustifolia aroma diminishes a state of wakefulness in the brain and helps individuals to fall asleep. Therefore, L. angustifolia aroma may have beneficial effect for female adults with sleep disorders.