The main goal of our research is to establish "methodology for investigation of event" and to construct "a knowledge reconstruction system" to provide event planners with "chances" to design effective and attractive events. The methodology described here is to articulate gaps between event planners’ intention and event visitors’ mental impression at real event sites. Visitors’ interactions with event objects were observed and their verbal reports (protocol data) and their actions were recorded with wearable computers and ordinary digital video camera, incorporation with Dentsu Inc. Their cognitive processes were analyzed with retrospective report method of protocol analysis. In this paper, we are going to describe the methodology adopted for investigating Visitors’ Mental Transition (VMT) in the real world and examples of obtained results. From analysis of the data, we obtained a prospect that our microscopic approach is useful and effective toward event-planning in the real world. Concepts and prototype of "knowledge reconstruction system" are described.