To solve the environmental problems, such as the climate change, many scenarios toward the sustainable society have been proposed. Scenario studies contribute to policy forming processes directed to these problems, and to visualizing the vision of desirable future. However it is necessary to clarify the causality or uncertainty described in scenarios, in order to create and understand these scenarios rationally. This paper proposes a structural description method of these scenarios. This method has two purposes. One is to develop a database of scenarios for supporting describing new scenarios. The other is to reuse simulators used in scenarios for analyzing the conclusions in the scenario. We describe scenarios by using three viewpoints; Scenario Level, Expression Level, and Word Level. This paper proposes structural description of scenarios on the Scenario Level and Expression Level and illustrates an example of structural description of scenarios.