The purpose of this study is to solve the difficulties in diagnosing the core competencies of undergraduate students and to develop a diagnostic tool for core competencies that undergraduate students must possess as talents required by society in the future. In this study, the core competencies of undergraduate students were defined as a disposition that synthesizes and utilizes knowledge, skills, and attitudes required as competencies. To develop the core competency diagnostic tool for undergraduate students, the study was conducted in three stages: (a) the initial questionnaire development stage, (b) the preliminary survey stage, and (c) the main survey stage, and 296 draft questions were developed through the review and use of existing survey tools and interviews with university students and HR managers. Content validity was secured by three experts in higher education. In a preliminary survey, as a result of an exploratory factor analysis of data from 914 undergraduate students, 59 question items were constructed for 14 factors. By analyzing the data of 8,968 undergraduate students in Korea in the main survey, discriminative validity, construct validity, and reliability were secured. As a result of a confirmatory factor analysis, RMSEA .077, GFI .935, IFI .951, and GFI .951 were confirmed to be suitable. As a result of the reliability analysis, the reliability was secured as .819-.895. The structure of the final core competency diagnostic assessment consisted of the 59 question items in the subjective development-related dimension, the object-related dimension, and the organization-related dimension. The subjective development-related dimension consisted of 19 questions related to self-comprehension, career comprehension, self-development, career plan, and self-management; the object-related dimension consisted of 22 questions related to 4 IR technology literacy, information processing, information retrieval, problem solving, and literacy; and the organization-related dimension consisted of 18 questions related to global, sympathy-communication, citizenship, and cooperation competencies. Based on this, suggestions for practice and subsequent research were made.