Purpose - The main feature of this study is understanding of the vendor's opportunism on the collaboration context between buyer and vendor from the buyer's viewpoint with resource dependence theory. A number of studies on opportunism have focused on opportunistic definitions and its theoretical studies. Other researches emphasize the importance of governance in ways that reduce opportunism. We think that this research could be filled with the lack of previous studies. Research design, data, and methodology - In order to accomplish research purpose, four hypotheses have been established based on the framework of resource dependence theory and previous studies. And we have used 599 survey data jointly collected by Korea Productivity Center and the Ministry of Trade, Industry and Energy. To verify these hypothesis, we have conducted multiple regression analysis with SPSS 23.0. Results - The vendor 's opportunism decreases as mutual trust with buyer becomes higher. However, as the degree of dependence of buyers on vendor resources increases, vendor's opportunism increases. And monitoring vendor's capacity has a moderating effect with buyer resource dependency to vendor's opportunism. Conclusions - This study suggest there are two options to decrease vendor's opportunism. Increasing mutual trust or decrease dependence on vendor's resources. Also, monitoring suppler's capacity could be effective when vendor's resource dependence is high.