Recently, map-based web platform service providing services are vitalizing and lots of information. And services are providing by the public institutions based on the publicness and reliability. However, there is inconvenience in user accessibility and usability in existing services. Therefore, a design plan for convenient system to find out the public data the user would like to want to find easily and correctly and use it effectively shall be found in this study. To this end, first, study the theory of map web platform service design through the documentary service including the theses, news and books and also study the elements and method for usability evaluation. Second, design the usability evaluation and improvement direction selecting map based web platform service of public institution. Third, analyze the effect before and after the improvement by the usability evaluation for improved web platform service. Lastly, would like to suggest the plan for interface design and user experience based on the analysis.