Objectives : The purpose of this study was to assess the effect of Taegeuk acupuncture on reducing mental stress by analyzing heart rate variability in Taeeumin. Methods : 16 Taeeumin-diagnosed healthy participated in this study. They were randomly divided into group A and group B. Each participant went through 3 sessions every week with 1 week of washout period in between each session. HRV was measured three times at every session; at baseline, after administering mentally stressful circumstances and after applying either one of simple rest, Taeeumin Taegeuk acupuncture or soyangin Taegeuk acupuncture. This study was designed as a crossover clinical trial. After same initial simple resting session for both groups at week 1, acupuncture for group A were executed in the order of Taeeumin Taegeuk acupuncture and soyangin Taegeuk acupuncture at week 2 and 3 respectively, with acupuncture for group B conducted in reverse order. Results : Simple rest, Taeeumin Taegeuk acupuncture and Soyangin Taegeuk acupuncture did show the significant changes in decrease LF(Norm) and increase HF(Norm) after stress stimuli. Taeeumin Taegeuk acupuncture, compared to Soyangin Taegeuk acupuncture, significantly decreased LF(Norm) and increased HF(Norm). Conclusions : This study suggests that Taeeumin Taegeuk acupuncture might be an effective means of stabilizing mental stress-induced imbalance of autonomic nervous system for Taeeumin.