This study describes the works on development of a scenario-based WBT system of electronic commerce to introduce and activate electronic commerce in our society because it is mostly required to correctly understand electronic commerce and timely educate its users and technicians for entering into global electronic commerce that binds every commercial area regardless of the borders and nationalities. This system, WBT(Web - Based Training of Electronic commerce), consists of two parts. The one part provides a general concept of EC. This is developed to meet the needs of beginner for EC. The other is a simulator for cyber shopping mall. It is designed for teaching how to shop at cyber shopping mall based on various scenarios. In addition, we can simulate ourselves for EDI, which enables trading partners to conduct routine business transaction, such as purchase orders, invoices and shopping notices with it. Our commitment to the development of this application is consistent with the objectives of being easy to learn electronic commerce and its applications in real world.