The purpose of this study is to conceptualize the definition of school readiness specific to the context of the Republic of Korea. The school readiness test can be used as basic data to enable early childhood educational institutes to determine the general readiness of preschoolers and provide support to fit individual characteristics. For this purpose, six stages of the school readiness development process were considered, that is, draft development, primary preliminary survey, primary expert verification, secondary expert verification, secondary preliminary survey, and main survey. In the main survey, tests were conducted using the school readiness final draft targeting 344 preschoolers living in Seoul and Gyeonggi-do. The item discrimination power analysis and factor analysis for the examination area and question area were also conducted. Consequently, a test tool was developed on the basic of the results obtained, consisting of 129 items in the five areas of knowledge, function, adaptation, tendency, and attitude. The knowledge area was divided into general, linguistic, and mathematical knowledge, and the function area into fine motor function, basic living ability, expressive function, and gross motor function. The adaptation area was classified into adaptation activity, separation anxiety, maladaptive behavior, and environment adaptation; the tendency area into learning tendency; others understanding, and individual tendency, and the attitude area into rule compliance and life habits. Keywords: school readiness, learning readiness, development of school readiness