Background: Although cranial electrotherapy stimulation (CES) is reported to have positive effects on mental functions such as depression and sleep improvement, detailed studies regarding awakening, attention and concentration among brain waves reflecting brain activity are lacking. Objective: To examine the effects of cranial electrotherapy stimulation (CES) on various electroencephalograms (EEGs) reflecting brain activities. Design: Randomized controlled clinical trial (single blind) Methods: This study selected 30 healthy adult women in their 20s who volunteered for this experiment. A total of 30 subjects were randomly assigned to three groups (Sham group, 0.5 Hz CES group, and 100 Hz CES group). EEGs were measured before and after the single CES, and the results were compared and analyzed. Results: The relative theta, alpha, and gamma waves indicated no significant differences in the interaction effects between time and group. The relative fast alpha wave only showed significant differences in the interaction effects between time and group in P4. The relative slow beta wave only indicated statistically significant differences in the interaction effects between time and group in T3 and T4. The relative mid and fast beta waves showed statistically significant differences in the interaction effects between time and group in all areas. Conclusions: These results suggest that a CES of 0.5 Hz awakens consciousness and has a positive influence on brain activity, while a CES of 100 Hz has a positive influence on thinking activity accompanying mental load during concentrating on one subject.