The purpose of this study is to understand the required concept in the architectural competition for public library and its application in design process. The research is based on the 27 design guideline of architectural competition for public library from 2009 to 2013 and, as a case study, the project for the Chungcheongnam-do Provincial Library, the prize winner in 2014. Three required concepts; symbolism, function, and sustainability, are categorized through the analysis on the design guideline of 27 competitions and are identified. Symbolism is expressed by landmark forms based on the local characteristics. The function of public library means to provide services to everyone, regardless of age, race, gender, religion etc., as a local community. Sustainability is related to passive architecture for the maintenance and management of buildings. These three concepts for public library applied on the design process of Chungcheongnam-do Provincial Library and design elements in each process are categorized in three concepts. The results shows not only how closely the locality and a user are related, but also the changes in the appearance of a public library as time passed.