This study analyses the level of resistance which workers have against the adoption of ERP systems and the factors affecting the resistance to the adoption of the new systems. The major results of the study include 1) about 40% of workers showed resistance to the adoption of ERP systems, and 2) all six factors (technical characteristics of ERP system, functional characteristics of ERP system, implementation approach, task changes caused by the adoption of ERP system, attitude toward change, and altitude toward organization) were proved to affect the resistance to the adoption of the ERP systems. In practice, adoption of ERP system brings significant changes to workers. In order for an organization to succeed, it is necessary to reduce the resistance of workers. Since this study is performed based on a case study, the results of the study may not be generalized. However, the results of the study may provide guidance which organizations can refer in the course of effective personnel management.