This article is intended to analyze how and on what a scientist “reflected” (defined in Adult Learning) in a science communication process. The method is a case study. The author participated in a project of a science cafe by a students’ group in JAIST, observed their planning, preparing, practice and evaluation processes, and analyzed when and on what the presenter reflected. As a result, the presenter reflected about the relationship among his study and the local area, his premises about the audience, problems of his presentation, research contents and organizational problems of the project. He reflected more in preliminary stages than after the practice, and most of his reflections were, sometimes unintentionally, for the success of his presentation and project. It is thought that a motivation to success science communication promotes reflections of a presenter. The results indicate that immense preparation for communication or continual communication is necessary for a scientist’s reflection.