The aim of this paper is to develop a network-based collaborative learning system based on cooperative learning, computer simulation, role playing, and web-based instruction, which is called NetClass. It is an educational system of hybrid-type, and supports three learning modes as a distributed network, a stand-alone system, or a web browser. To accomplish the purpose of this paper, we have studied on the following topics. First, we selected appropriate learning contents among dilemmas on information ethics. Second, a Collaborative Dilemma-solving Learning Model (CDLM) was designed, and this model means systematic procedures that leaners can notice others' feeling and thinking and predict the results of his actions by introducing interactions among learners on computer networks. Third, Collaborative Learning System Model based on standard architecture of an educational system was proposed. Fourth, we developed many components such as network components, database components, and interface components.