It has gradually been recognized that the juvenile should be treated differently from the adult in the criminal justice system. This recognition gave birth to juvenile court movement at the beginning of 20th century. Juvenile court and juvenile law made substancial, not only normative, solutions possible to the problems of juveniles involved in the criminal justice system. But these innovations have been accompanied with negative phenomena, for example expanded interventions by the state powers. In Japan, juvenile law achieved the standard of the world relating juvenile laws by the enactment of the present law in 1948. Family court has juris diction over juvenile cases. The court attempts to solve juvenile problems individually and substancially. It proposes policies in such fields of education, child welfare, police and public prosecution. It has assistant organs of its own, which are agents called investigators of family court. Activities of family court investigators to enhance welfare of children and juveniles is called "judicial welfare." The concept of "judicial welfare" demands scientific ability of the staff who apply the juvenile law. On the other hand, an objective of judicial "welfare" appeals to competent persons who have scientific ability. Secondly ability of fact-finding is necessary for "judicial welfare." Satisfaction of the abovementioned conditions will combine judicial functions with the functions of welfare of juvenile justice, and will upgrade the juvenile justice on to the higher level.