Objectives : This study was performed to find the desirable remaining time of needle in the acupuncture treatment. Methods : The 21 volunteers were given acupuncture at LU9 vertically and needles were remained for 2 min, 10 min, 15 min, 30 min, respectively. The thermographic change induced by acupuncture was measured with Digital Infrared Thermographic Image at the following acupoints: LU11, LU10, LU9, LU8, LU5, LU1, and PC7. The statistical significance of thermographic change was evaluated using paired t-test and post hoc Wilcoxon test. Results : The most significant changes after acupuncture were produced when needles were remained for 10 min or 15 min. LU11, LU5, LU1, and PC7 were the point at which all of the remaining time produced significant change commonly. At LU11, the biggest change was produced when needle was remained for 15 min, while at LU5, LU1, and PC7, the biggest change was produced when needle was remained for 30 min, and the smallest change was produced when needle was remained for 10 min at all of acupoints of LU11, LU5, LU1, and PC7. The unbalance between left side and right was decreased the most largely in 15 min group. Conclusions : The results of this study suggest that the desirable remaining time of acupuncture needle might be 15 min.