This study aims to look for care quality factors reduce the daily stress of young children placed in care centers for long hours. Therefore, the research questions look into how the hours and care quality factors in child care centers affect young children's daily stress, and whether the care quality factor moderates the impact of the hours children spent in centers. The subjects in this study were 380 children from 3 to 5 years old from 10 child care centers. The Korean Preschool Daily Stress Scale(KPDSS) for children's daily stress and Early Childhood Environmental Rating Scale-Revised(ECERS-R) for quality of each classroom of centers were implemented. The main findings were summarized as following: (1) The more hours he/she spent in the center, the more stress he/she had. Children who spent 9 hours or more had more stress than children with 7 hours or less. (2) Among the 7 quality factors including space and furnishings, personal care routines, language reasoning, activities, interaction, program structure, parents；staff, the interaction level between a teacher and a child and the level of parents and staff had the most impact on children's daily stress. (3) The qualitative factors of child care, language reasoning level, interaction level, parental support, and level of teachers reduced children's daily stress which was affected by the hours they spent in centers. Thus in order to reduce the daily stress of children who attend more than 9 hours a day, it is crucial to promote language reasoning activities and interaction between teachers and children and to improve parental support and teachers' professionalism. .Key Words : daily stress, moderating effects, quality, child care center.