Objectives : This study was to investigate the short time effect of caffeine on heart rate variability(HRV) and the effect of Neiguan(PC6) acupuncture stimulation on HRV. Methods : 27 healthy adult volunteers were randomly allocated to two groups: Neiguan group (N=13) or placebo group (N=14). The study was carried out under a randomized double-blinded placebo-controlled trial method. Each group orally received the same tablets with 200 mg caffeine. After 1 hour, acupuncture was applied to the Neiguan(PC6) points for the Neiguan group, and for the placebo group was applied to a non-acupuncture point. Both groups were estimated with HRV 3 times, before and after caffeine ingestion, 20 minutes after acupuncture stimulation. Results : After taking caffeine, pulse rate, mean-HRV, and pNN50(the proportion derived by dividing NN50 by the total number of NN intervals) decreased, SDNN(standard deviation of all normal-to-normal (NN) intervals), RMSSD (the root square of successive differences), TP log, HF(high frequency), and HRV index was increased. There were significant changes to the autonomic nervous system after taking caffeine. There were no significant differences between the two groups after acupuncture at Neiguan. Conclusion : Caffeine could induce general activation of the autonomic nervous system. Neiguan acupuncture stimulation may not have significant influence on the autonomic nervous system.