Business processes, such as workflows, are software, too. However, development, evolution, and deployment of business processes have different difficulties from general software. Control, introduction, evaluation, and testing of business processes are difficult because multiple processes are related to each other and many people are involved in processes.To solve these problems, we propose BPT/BPR/BPS (Business Process Tactics, Reengineering, and Simulation) lifecycle, based on multi-agent groupware model. BPT means activities to control processes dynamically, which we have already proposed. In this paper the simulation phase is mainly focused. We give a simulation model which has some original aspects, and show a prototype of simulation tool.