This study is based on the premise that preventing juvenile delinquency in advance is the best and the most effective way of preventing it from ever happening. The purpose of this study is first to develop a barometer to diagnose and measure the risk factors on a student. It is known that risk factors may increase the possibility of juvenile delinquency. The author made a survey of nine hundred and thirty one students, which consists of both middle school 2nd graders and high school 2nd graders (8th and 11th graders). The author examines their risk factors. As a result, he comes to the conclusion as follows. First, most important risk factors include depression, anti-society sentiment, impulsive nature, aggressive nature, negative family economy, family trouble, delinquency bond, discrimination from teachers, and an environment of tolerating delinquency. Second, in general, following types of students were found showing higher risk factors: male students, high school students, students with single parent, students with father in non-specialized job, students with father possessing less than bachelor’s degree, students with mother possessing less than bachelor’s degree, students with family renting a place to live, and students without religion Based on the study above, the author suggests ways of reinforcing protective factors to prevent juvenile delinquency. To reduce the anti-society sentiment, it would be effective to use a self-esteem enhancement program, mentoring program, parent education, family healing, teaching of parent roles, teacher’s personality development, volunteer program, and so on; to reduce the depression, it would be effective to use self-esteem enhancement program, mentoring program, parent education, family healing, and teaching of parent role; to reduce the impulsive and aggressive natures, it would be effective to use self-esteem enhancement program, mentoring program, parent education, family healing, teaching of parent role, and anger- control program; to reduce family trouble, it would be effective to use parent education, family healing, teaching of parent role, and the program for substituting family roles; to reduce the negative family economy, it would be effective to use parent education, family healing, teaching of parent role, and low-income family supporting program; to reduce the delinquency bond, it would be effective to use self-esteem enhancement program, and teacher’s personality development program; to reduce the discrimination of teachers, it would be effective to use teacher’s personality development program and the program of interference of School Social Worker and to reduce the environment of tolerating delinquency, it would be effective to use self-esteem enhancement program, parent education, quitting of smoking and drinking program, campaign or education program for the community. In conclusion, preventing juvenile delinquency is seriously affected not only by an individual juvenile, but also by the environment around the juvenile. Therefore, we should consider changing and improving the environment for the juvenile in a governmental policy scale. We should always analyze their environment proactively and then should endeavor to exploit more effective protective factors, whether they are related to individual, family, school, friend, or the community. At the same time, we should try very hard to correctly intervene at all times in arising social welfare cases. This would be possible only by having inclusive and effective access to the community.