We examined the social mobility of social classes between a birth and a high school graduation, and between a high school graduation and an employment before estimating determinants of Korean SAT score and income after getting a job, using KEEP. Empirical findings are as follows: first, a similar pattern is found in the trend of social mobility between a birth and a high school graduation, and between a high school graduation and an employment after college. Second, the secondary education exerts a positive influence on social mobility, but the higher education does not. Third, with respect to determinants of SAT score, the education level of parents, learning related variables, and personal factors impact on the SAT score, and this is similar to those determinants identified as affecting social mobility between a birth and a high school graduation. Fourth, it is found that income increases with a company size, a working period, a regular employment, personal factors, as well as an internship experience with a statistical significance. Especially, the coefficient for a regular status influences the greatest. Fifth, estimation of determinants for an upward movement in social mobility shows that a positive impact is had when it is a male, the working period is long, the company size is big, and when in regular employment with a statistical significance. These findings imply that acquired factors, like efforts made by individuals, are more important than exogenous environmental components in determining individuals’ social mobility.