The purpose of this study was to inquire the relationship between principal's transformational leadership and teacher's organizational commitment. The study methods were adopted literature review and questionnaire. The subjects included 1062 teachers from public elementary schools. The collected data were analyzed by descriptive statistic, one-way ANOVA. Pearson product-moment correlation, and multiple stepwise regression analysis. Conclusions were made as follows: 1) The general situations of principal's transformational leadership and teacher's organizational commitment are good. 2) There is a positive correlation between principal's transformational leadership and teacher's organizational commitment. 3) Principal's transformational leadership will result in better teacher's organizational commitment. 4) Formulating vision is a major aspect to effectively explain teacher's organizational commitment. Based on the result, this study has provided some suggestions for school principal, teachers and future study.