The purpose of this study was to develop a scale for understanding the factors that affected sport fans following a team. The participants were 244 sport fans in Professional Baseball. They were asked to respond to a scale containing 19 items. The inventory was structured by item analysis and factor analysis, the outcome showed that the scale was composed by ”significant others”, ”successful and famous”, ”popular traits”, ”economic reasons”, ”familiar reasons”, and ”geographical reasons”, which accounted for 56.8% of total variance. The results revealed that the scale was reliable and valid and it can be used for the future study.