Objectives : This study was performed to investigate the effect of simple acupuncture and electroacupuncture at Bai Hui($GV_{20}$) on heart rate variability in healthy adults with stress task. Methods : 40 healthy volunteers participated in this study. HRV was recorded before and after stress. And then simple acupuncture(SA group) was applied at $GV_{20}$ or electroacupuncture(EA group) was applied at the same spot in each treatment group for 20 minutes. No treatment was performed in control group for 20 minutes. Then HRV was recorded. Results : 1. In all groups, LF norm, LF/HF, HF norm showed significant changes after mental stress. 2. Control group showed no significant change. In SA group, HF norm LF, LF norm and LF/HF showed a significant change after treatment. In EA group, Mean HR, HF, LF norm, HF norm and LF/HF showed a significant change after treatment. In both treatment groups, there were significant differences after treatment compared to control group. 3. In EA group, HF and HF norm decreased significantly after treatment compared to SA group. Conclusions : These results suggest that simple acupuncture and electroacupuncture at $GV_{20}$ affect the balance of the autonomic nervous system and that electroacupuncture at $GV_{20}$ enhances parasympathetic activation more than simple acupuncture.