Objective : The study was to find out the effect of sleep disorder bt melatonin when we applied the evironmental change to rats wirh sleep disorder. Methods : We performed the study in lab which is located in Gyungbuk. We divided 26 rats into two groups. The experimental group had the environmental change for 3 days. The control group didn't have the change. We checked the level of melatonin of each group. Results : There was a significant difference of the level of melatonin in experimental group after applying the environmental change for 3 days (p=.000). The level of melatonin was increased a little for 3 each day in control group, but there was no significance(p=.212). There was a significant difference of the level of melatonin in both groups before and after applying the environmental change. However, the level of melatonin was increased significantly in experimental group, and the level was decreased significantly in control group. Conclusion : The patients with sleep disorder are increasing in modern society. We made a animal model with sleep disorder to find out the effect of the environmental change. We applied the environment like human's and could know the improvement effect of sleep disorder.