Background and Objectives: Insomnia is one of the most common sleep disorders in the world and affects as much as 10% of the general population. Schumann resonance (SR), earth’s fundamental frequency of electromagnetic field, is believed to have much effect on human physiology. The purpose of this study is to evaluate the effectiveness of SR emitting sleep device as non-pharmacological therapy for insomnia. Materials and Methods: Thirty-seven participants with Pittsburgh Sleep Quality Index≥5 and Korean Version of Insomnia Severity Index≥8 were recruited in a single institute from September 2021 to July 2022. The participants completed sleep diaries for 2 weeks, without the use of SR sleep device in the first week, with the use of the device in the second week. The data from the sleep diaries between the 2 weeks were analyzed. Results: During the week with use of the SR sleep device, the total sleep time was increased (p=0.084). Furthermore, sleep latency, number of arousals, and total duration of arousals were markedly decreased significantly (p=0.003, p=0.018, and p=0.034, respectively). Score of feeling refreshed as well as overall sleep quality score significantly improved compared to the week without the use of the device (all p〈0.001). Conclusion: SR sleep device may improve subjective sleep quality of patients suffering from insomnia.