Due to change in management environment and paradigms, companies need to the open management system that provides information for real-time costing, customer satisfaction, decision making support, responsibility management etc. We are not ready to implement this system yet. But we must introduce a new management system, i.e., ABMS(Activity- Based Management System) on the basis of the ARC(Activity-Based Costing) by development of production/information technique. This paper realizes foundational concepts of Activity and ABC, reestablishes the concept of ABC correctly and expands ABC for ABMS. Thus this paper is useful for ABMS modeling, leading competitors, total productivity improvement and strategic management for the best quality and service.