The purposes of the present study were to explore experiential factors affecting the feeling of trust, and to search for a way to encourage the development of trust. Using either the free description or SCT method for 48 helping professionals (teachers and school counselors) and 102 high school students, a 64-item test was prepared to measure experiences affecting trust. The items and trust scale were administered to 456 high school students. The result of the factor analysis showed that experiences affecting trust had 4 dimensions:“experience of acceptance”,“experience of approval”,“experience of deep attachment with parents” and “painful experience from personal relationships (negative effect)”. Furthermore, experiences affecting trust for 160 high school boys and 71 male high-school aged delinquents were investigated. Multiple regression analysis showed that delinquents' trust was mainly affected by experiences of approval and acceptance by adults, and that of regular high school boys by peer approval and experiences of personal-accomplishment. It was suggested that the path to self-confidence in adolescence follows a gradual shift in the locus of acceptance from adults to peers, and finally to self-acceptance.