Purpose: The purpose of this study was to identify the quality of sleep and its influencing factors on the institutionalized elderly. Methods: The respondents were 145 institutionalized elderly in Daegu and a structured questionnaire was used for data collection, which was conducted from February 10 to 28, 2007. The questionnaire was the Yi(2004) quality of sleep scale. All the information was collected through face-to-face interviews, using the questionnaire. The data were analyzed by SPSS/WIN 12.0. Results: The results of this research were as follows: First, the mean for the quality of sleep in the institutionalized elderly was 83.92. Second, in the subscales of the quality of sleep scale, the mean for daytime dysfunction was 40.35; for restoration after sleep it was 10.43; for difficulty in falling asleep it was 11.00; for difficulty in getting up it was 8.88; for satisfaction with sleep it was 8.62; for difficulty in maintaining sleep it was 4.75. Third, the factors influencing the quality of sleep were economic status, perceived health status, and pain. Conclusion: Based upon the findings above, this study provides useful information that could assist in improving the quality of sleep among institutionalized elderly, and indicates that nursing intervention is needed.