The importance of SIS (Strategic Information System), which supports strategic business operation, has been increasing with the progress of information and communication technology. In SIS, the close connectivity between information and business is a critical success factor. In this paper the authors propose a methodology of planning SIS. First, introducing the business information system diagram, the role of information for business is clarified. Next, such concept is introduced that the information power as effectiveness for business is determined by the connectivity between information quality and information field representing the necessity of information. On the basis of this concept, a methodology of planning SIS, which consists of 3 factors, that is, steps, tools and frameworks, is proposed. The characteristic of the proposed methodology is to find a solution to the complex problem of planning SIS systematically by employing fixed steps, fixed tools and fixed frameworks.