This research proposes a Web-Service that supports the interpretation of the local environment objectively through visualized spatial information, and evaluation of the value subjectively through interactive interfaces. This article focuses on the livable environment whose criteria have become diversified in recent years. In order to highlight such varieties of values during evaluation, the proposed system, LEES (Livable Environment Evaluation-support System) aids exploratory evaluating process by: 1) clarifying ambiguous preferences of livability using a Fuzzy Structure Model, 2) analyzing areas using multi-criteria according to the individual preference structure, and 3) visualizing distributions of the results for supporting decision-making. In order to validate this system, sensitivities of typical preference scenarios are analyzed. Additional uses of this Web GIS-based system are also discussed. An empirical study directly involving citizens is in progress to improve the social effectiveness of the system.