The purpose of this study is to investigate the relationships between institutional pressures and IT investment decision making of management. To analyze the proposed model, we distribute survey questionnaires to mid-size IT firms and collect data from them. Furthermore, the proposed model was tested by PLS(Partial Least Squares) technique. We found that coercive pressure and normative pressure have an effect on mimetic pressure. However, these two pressures do not influence the IT investment decision making. The mimetic pressure has an effect on the IT investment decision making. The conclusions and implications are discussed.