The Sleep Quality Questionnaire was developed and its reliability and validity were estimated. Four samples involving approximately 1400 Japanese college students and employees were used to examine the factor structure, the test–retest reliability, convergent validity, and incremental validity. Sleep Quality Questionnaire scores were associated with well-being, such as general health states, depressive symptoms, chronic fatigue, and quality of life. Test–retest estimates indicated that Sleep Quality Questionnaire scores were stable over an 8-week period. The Sleep Quality Questionnaire incrementally contributes to well-being even beyond the Epworth Sleepiness Scale and to sleep duration. Overall, the data suggest that the Sleep Quality Questionnaire scale is both reliable and valid.