The purpose of this study was to investigate the structure underlying performance of "good situational decision-making" from the viewpoints of tennis coaches. The specific aim of preliminary investigation was to explore detailed examples of "good situational decision-making" in coach's perception. As a result, it was found that coaches perceived performance of "good situational decision-making" was derived from acknowledging the level of one's own ability, using appropriate situational decision-making based on comparison and analysis of their own ability to the opponent's ability, immediately and precisely deciding performance, and accomplishing it. Thepurpose of the main investigation was to clarify factor structure anderlying performance ot "good situational decision-making" in coach's perspective. We developed a 60-item questionnaires based on the findings from preliminary investigation, and sent them to participants by mail. As a result, five factors such as performance appropriate for given situation, accomplishment of one's performance, recognition of situation, immediate judgement and prediction, and analysis of opponent were derived. From these findings, it was indicated that "good situational decision-making" includes not only demonstrating performance that is appropriate gfor given situation, but also internal information processing should be precise and continuous. Thus, it was revealed that performance of "good situational decision-making" is associated with not only accomplishment of performance that is appropriate for given situation but also the ability to analyze in advance, predict, and judge immediately.