This study aims at developing the Mathematical Epistemological Beliefs Scale (MEBS) suitable for elementary school teachers by evaluating its reliability and validity. The analysis consisted of two phases: pre-test and test. Both phases adopted stratified sampling method with elementary teachers of 251for the pre-test and 439 for the test respectively. Through exploratory factor analysis and confirmatory factor analysis, four factors were found: simplicity of knowledge, certainty of knowledge, source of knowledge, and justification of knowledge. The internal consistency of the Cronbach´s alpha of the MEBS was .80 for the total score of the 13 test items, which shows the high degree of reliability of the MEBS. This study further investigated the measurement invariance of the test. The results indicated that the same construct is being measured across different genders of the elementary school teachers, which confirmed high level of construct validity of the MEBS.