This paper attempts to examine how social trust influences human capital formation using prefectural level data in Japan. To this end, I constructed a proxy for social trust, based on the Japanese General Social Surveys. After controlling for socioeconomic factors, I found that social trust plays an important role in reducing the rate of long-term truancy in primary and junior high school. Results suggest that social trust improves educational quality. (Contains 5 tables and 2 figures.)