In order to improve the quality of life by maintaining healthy mind and sleep, there are a variety of psychological therapies and relaxation methods spreading through the rapidly changing society. This study aims to examine the effects of Yoga Nidra, physical, emotional, and spiritual method of relaxation, on mind and sleep. A number of women who live in Seoul were recruited and the experimental group practiced one hour of Yoga Nidra two or three times per week for 8 weeks, for a total of 20 hours, whereas the control group did not have any treatment. The participants who were included in the final analysis are 10 in the experimental group and 8 in the control group. The measures that are used for the analysis of effectiveness of Yoga Nidra were quality of sleep, anxiety, and depression. The two-independent samples t-test were used for the statistical analysis. The findings of the study are as follows; First, there was a significant increase of quality of sleep of the experimental group, in comparison with the control group. Second, there was neither a decrease of anxiety of the experimental group nor a difference between the two groups. Third, there was a decrease of depression of the experimental group, and yet there was no significant difference between the two groups. This study shows that Yoga Nidra supports sound sleep by improving the quality of sleep and is an effective way of keeping the mind healthy by reducing depression. Therefore the study proves the positive effects that Yoga Nidra has on sound sleep and emotional health of adult women.