The purpose of this study is to examine the determinants of union commitment and union participation intention based on the social exchange perspective and apply implications to union setting to improve union management. The results are as follows : Firstly, union commitment is the most direct predictors of union participation intention and mediates the relation both perceived union support and union instrumentality and union participation intention. Secondly, both perceived union support and union instrumentality are direct predictors of union commitment but perceived union support has more effect than union instrumentality on union commitment. Lastly, process related justices affect on perceived union support but interactional justice is a more Important antecedent of perceived union support than procedural justice. Unexpected finding is that union instrumentality has direct relationship with not only union commitment but also perceived union support. This finding is needed further research in the future.