Teacher efficacy has been shown to be a powerful construct related to student achievement, school improvement, and education innovation. The research of this construct has born much fruit in the field of education. And yet there remains a lack of clarity in the concept and structure of teacher efficacy. Based on the self-efficacy theory developed by Bandura (1977) and the integrated model of teacher efficacy proposed by Tschannen-Moran, Hoy, & Hoy (1998), this study explored the concept and measurement of teacher efficacy. A sample of 415 primary teachers in Taiwan was administered an efficacy questionnaire adapted from the Teaching Efficacy Scale (TES). Factor analysis revealed that teacher efficacy is multidimensional in nature, comprising six factors : instructional efficacy, classroom management efficacy, efficacy to assess learning progress, efficacy to communicate with parents, efficacy to enlist teaching reform, and efficacy to change environment. The TES developed in this study differs from measures of teacher efficacy found in previous research, this study employed six dimensions of efficacy rather than separated subscales for personal teaching efficacy and general teaching efficacy. These results supported that teacher efficacy is a multidimensional concept, thus has implications for both theory and practice. Finally, the issues in the concept, measurement, structure, and application of teacher efficacy are discussed.