This study mainly investigated which mental state of designers, self-confidence or sense of inferiority, has positive effects on professional design achievement. This study attempted to find if there is correlation between designers' self-confidence or sense of inferiority and their professional achievement. With regard to the tendency of designers' psychological state, the Rosenberg Self-Esteem Scale was used to measure designers' selfconfidence, and statistical computations were made based on gathered data. This study used correlation analysis to find if confidence level of 46 seniors of Design Department is relevant to their professional achievement. The results of the study showed that confidence level of designers has a slight correlation to professional achievement. Factors leading to the study's findings may be the small amount of sample analyzed or may be the reason that the Rosenberg Self-Esteem Scale only detected the current level of self-confidence and could not give a proper feedback on designers' self-confidence during the entire semester. In the future, the results of this study can be considered as a pre-test experiment for a more complete study, and it is expected that results of the study can be for design educators' reference.