For the purpose of applying Information Technology for the dilemma of environmental issues, an argument model useful for visualizing the logical structure of argument process is devised so that it can enhance the self-learning ability through the argument process, and it can also develop the ability of value judgement from versatile aspects of the environmental issues. On the basis of this model, the argument support system of network community type, named ¡ÉERDE¡É was developed, and applied to the classroom education in a high school. As a result, the students had argued effectively about a given theme using ERDE. From the questionaires, the students had evaluated positively the educational effect of ERDE.