Public Libraries should be open at times when the community can make the most effective and convenient use of library collections and services. In other words, public library must provide adequate open hours for local residents. In this respect, this study analyzed the minimum opening hours per week in public library standards of international organizations(IFLA/UNESCO) and major countries (USA, Canada, UK, France, Australia, China, Taiwan, Japan, Korea) and suggested a desirable minimum standards(under 10,000 population-45 hours ; over 10,000∼20,000 population-50 hours ; over 20,000∼50,000 population-55 hours ; over 50,000∼100,000 population-60 hours ; over 100,000∼300,000 population-65 hours ; over 300,000 population-70 hours) for opening hours per week of public library based on population size in Korea.