Background: Alopecia areata is an autoimmune disease characterized disease by round alopecic patches. Follicle specific T helper 1 cell-mediated autoimmune reaction is considered most important reaction. There are many case reports on 308nm excimer laser therapy for alopecia areata, however there are few studies using side-by-side method. Objectives: The purpose of this study is to evaluate therapeutic effect of 308nm excimer laser therapy in 10 patients of alopecia areata and to analyze the results. Methods: We measured MED on alopecic patch in advance then we radiated laser to the right half of the lesion (MED-50mJ). We treated twice a week for 12 weeks. We took photos and analyzed phothotrichogram monthly. Results: 2 of the 10 patients were dropped out. In treated area, the number of total and vellus hair were statistically increased after excimer laser treatment(p=0.018, p=0.043). But, there were no statistical difference between treated and control areas. In treated area, the diameter of hair shafts were significantly increase after excimer laser treatment(p=0.012), also, there were statistical difference between treated and control areas (p=0.013). There were no significant side effects after excimer laser without mild erythema. Conclusion: We found that the preliminary clinical trial showed regrowth of hair. These results showed that excimer laser has a therapeutic effect on alopecia areata, large scale of clinical trial will clarify the effects and safety of the excimer laser.