This paper empirically investigates the social exclusion of non regular workers in Japan by conducting an internet survey of non regular workers on a national scale. Based on survey data, indexes were created to measure 7 types of social exclusion. We then categorized respondents by employment status and ran regressions to find the determinants of social exclusion. The results show that day laborers are socially excluded and temporary workers in the manufacturing industry have a conspicuous lack of social relationships. After controlling for individual characteristics, we find that differences of social exclusion are caused not by employment status but by the shortness of contract term and the fact that these workers work in the manufacturing industry. Employment history and experiences at school have a significant effect on the degree of current social exclusion. We also find that social exclusion indexes are positively correlated which implies that multiple social exclusions occur.