The purpose of this study was to examine the effect of acupuncture on trunk flexors compared with trunk extensors in patients with chronic low back pain. The experimental group was treated with acupuncture on trunk flexors. The control group was treated with acupuncture on trunk extensors. Acupuncture treatment was performed 12 sessions over the course of 6 weeks. Volunteers who satisfied the requirements were enrolled in the study. Chronic low back pain was evaluated based on the VAS for bothersomeness, VAS for pain intensity at every treatment and 8, 12 and 24 weeks after starting the treatments, and ODI, SF-36 and BDI before and after treatments and 8, 12 and 24 weeks after starting the treatments. The VAS score for bothersomeness significantly decreased after treatment for up to 24 weeks after starting the treatments in both group (p<0.05). The VAS score for bothersomeness in the experimental group decreased more rapidly than that of the control group with statistical significance (p<0.05). The VAS score for pain intensity, ODI, SF-36 and BDI significantly improved after treatment for up to 24 weeks after starting the treatments in both group (p<0.05). The VAS score for pain intensity, ODI, SF-36 and BDI in the experimental group showed more rapid improvement than those of the control group. But, there were no statistical significances. Treating trunk flexors using acupuncture was more effective in decreasing the degree of bothersomeness caused by chronic low back pain than treating trunk extensors with acupuncture. There is a need to perform further studies.