Web service technology will be used in various business fields and it will affect business paradigms. But, however, there is no standard so far and we have many problems to be solved in order to insure interoperability and security. Especially we have to solve Web service security for effective utilization of the technology and otherwise, the technology will not be used in the business field. We, therefore, need to develope security technology which fits to the Web service characteristics. This document describes a proposed strategy for addressing security within a Web service environment based on the results of analysis on the Web service security problems.