The purpose of this study is to investigate the relationship between job discretion and participation in learning, to analyze the variating relationship by learning type, and to examine the moderating effect of educational mismatch on the relationship. Job discretion is desirable for securing flexibility in decision-making and problem-solving, but it can cause moral hazard and is recognized as a double-edged sword. This study is anchored on the fact that the freedom of choice and the expansion of the scope given by job discretion remove obstacles to learning, but may affect the willingness and attitude to participate. Although over-education continues to be an issue in the use of social manpower, few studies on the relationship between over-education and participation in vocational training have been conducted. This study investigated the effects of job discretion and its interaction from the perspective of job maturity, which sees educational mismatch with the concept of demand and achievement in general job skills. In this study, a logistic regression model was established using PIAAC 2012 data and analyzed in a controlled state of cognitive and non-cognitive abilities. The results of the study show that while job discretion has a curve-linear relationship in formal learning related to vocational education and training, it has a linear relationship in non-formal learning. Education mismatch moderates the relationship between job discretion and learning participation in formal learning, whereas in non-formal learning, only the main effect of educational mismatch is significant. The interactive effect of job discretion and educational mismatch suggests that expanding job discretion can be a way to increase productivity in our society where over-education is expanding.