Toward understanding developmental processes whereby the Japanese male adolescent enters and establishes an early vocational career, a set of panel-data consisting of 317 male college graduates derived from a larger, longitudinal national survey was analized. Patterns in the changes of vocational suitability perceived by the 317 panels at their three chronological age points (15, 18, and 26 years old) were examined. An intraindividual change was observed to occur between the point of age 18 and the point of age 26 (between before and after their entry into vocational careers). There was almost no change for the time from 15 to 18 years old (for the time before their entry into vocational careers). With this basic pattern, an interindividual difference was found to emerge where the panel was compared each other in terms of the disciplinary field majored at college (a difference between humanities and social science majors and engineering and natural science majors). For these findings, implications are presented in relation to the broader education-acquiring system in contemporary Japanese society.