The fact that EDI is the IT system between partners implies the importance of studying the affecting factors associated with partnership in EDI. But there are few researches about the inter-organizational factors related to the relationship between partner firms, so called partnerships, influencing the implementation of EDI. Therefore our research is to investigate the relationship between partnership and EDI implementation with inter-organizational perspective. Additionally, we investigate the moderating role of EDI adoption attitude when the companies are divided into two groups, proactive attitude and reactive attitude. As a result, first, we found the positive relationships between the partnership factors about partnerships among trading partners and the degree of EDI implementation. Second, we expected that proactive firms have stronger significant relationships than reactive firms, but only the relationships between interdependence and integration, interdependence and utilization and trust and integration were proved to be signigicant among ten relationships. Third, we found positive relationships between EDI adoption attitude and EDI implementation.