Artifact's reusability should be enhanced, because a social system of mass-production/consumption causes many environmental problems. However, there is no methodology that improves artifact's reusability and adaptability, covering the whole artifact. The main purpose of this research is to construct the design methodology for sustainable society by using "Latent Function". Latent Function is defined as a new function appeared when artifact's surroundings changes. If an artifact has many Latent Functions, it becomes usable succeedingly. In this paper, we propose the method of estimating abundance of Latent Function in order to analyze its characteristic.