Nowadays enterprise resource planning (ERP) systems are worldwide a standard solution implemented in a great number of manufacturing companies worldwide. The implementation of an ERP system is performed to integrate business processes, allocate company’s resources efficiently and provide important data for decision support. Implementing an ERP system is expensive and time-consuming. Therefore a great number of research activities are focused on key success factors of ERP implementations. But what does a successful implementation of ERP system mean? If an ERP project was completed according to the schedule, the budget was not exceeded and the scope was realized, it means that the implementation was successful? Implementation of an ERP system is a long-term undertaking, and not only a short-term project that is finished just after the system installation. Especially for a project driven enterprise that realizes engineer-to-order production, the evaluation should encompass a long period of time. In the article a methodology based on ERP data analysis and end users’ satisfaction is proposed. This research is based on a real data, extracted from ERP system of a polish company that realizes prototyping production in the area of machine tools construction.