Currently most of the workflows in enterprise business processes are implemented and managed as information system. However, workflows between organizations are still processed manually based on paper document because it is difficult for the organizations to trust the process and the result of workflow in the system which is provided by one of the organizations or a third -party organization. In this paper, a system architecture for cross organizational workflow management utilizing blockchain technology is proposed. It eliminates every Single Point of Trust (SPoT) which causes falsification risk of the process and data. Our proposed system architecture is considered to connect with internal workflow management system and accommodates two types of smart contracts for interorganizational workflow definition and interorganizational workflow processing, which validates related data in every transaction. By this architecture, each organization can be aware of the data falsificat ion when the data on one of the organization nodes is falsified by a malicious workflow administrator or a system administrator. Through the implementation of the proposed system and evaluation of the falsification risks based on the attack scenarios along workflow life cycle, it is confirmed that all the risks are avoided by the proposed system architecture.