As industry pursues the appropriate management of chemical substances, voluntary efforts to manage environmental and human health risks are required in middle-stream industries that manufacture components in the product supply chain. In this study, an activity model was developed as a framework of process improvement for risk reduction in order to support risk management in processes operated in middle-stream industries. Problems in the current risk management activities were analyzed in a case study of cleaning processes of metal components, and framework requirements were clarified on the basis of the problem analysis. Three activities, namely, process design based on quantitative evaluation, mechanism development for process evaluation, and constraint management related to decision making in process design, are needed for risk management in middle-stream industries; and each activity requires different authority and abilities. A practical framework defining the actors of each activity was developed with the activity modeling method IDEF0. Sub-models were created for project administrators, engineers, and researchers; and information flow among sub-models was depicted in order to define collaboration among these actors. The activity model developed can be applied to risk management as a guideline for middle-stream industries that lack the necessary knowledge or know-how for risk management.