The purpose of this study was to explore critical success factors inducing practical startup challenge through individual startup internship of university students, identify factors influencing startup internship, and derive critical success factors from the relationship between such influential factors and practical startup challenge. Startup internship system is a program designed to support startup site operation in order to increase probability of success in business startup by helping build up experience with practical startup and overcome fear of failure based on performance of works by university students at the site of startup venture. We looked into the factors influencing the performance of startup internship to promote startup internship system that has been recently introduced. For analytical methodology, we used consecutive mixed research model incorporating both qualitative study and quantitative study. In relation to qualitative study, one-on-one interview was performed of 5 experts in startup education in order to identify factors influencing startup internship. In connection with quantitative study, 143 university students were surveyed based on variables identified in qualitative study. Based on results of analysis, the qualitative study derived 5 factors such as startup expertise and capability, startup internship management system, preparation for foreign language proficiency and capability, global competency improvement and practical startup challenge, etc. For quantitative study, the results of multiple regression test of variables showed that startup expertise, capability, and startup internship management system had a positive(+) causal relationship with global competency improvement while startup expertise and capability exhibited a positive(+) relationship with practical startup challenge. In addition, improvement of global competency had a positive correlation with practical startup challenge. Both startup expertise and capability were found to have high standardization coefficient for global competency improvement and practical startup challenge and therefore were considered as very important variables. Particularly, startup expertise and capability had high standardization coefficient for practical startup challenge, implying that both startup expertise and capability factors played important role in startup internship. The results of this study suggest that successful operation of startup education, such as startup internship, etc., would become more likely when factors related to startup expertise, capability, and startup internship management system are considered and provided in developing and utilizing the startup education, such as startup internship and carrier guidance programs.