This study aims to explain the stages of developing a Holistic assessment instrument for the competence of prospective mathematics teachers based on constructs from several literature reviews to measure the competence/ability of prospective mathematics teachers. This development goes through 8 steps of developing non-test instruments. Validity and reliability of instrument traced from 101 students. The initial instrument design carries out initially, then validated with the Aiken formula by 14 experts. The series of initial stages obtained 30 instruments ready to be tested from the original 40 items. The second stage is to perform a confirmatory factor analysis (EFA) followed by testing the construct and convergent validity and looking for the reliability coefficient with confirmatory factor analysis (CFA). The results of the EFA produced 28 items become into four factors, namely pedagogic content knowledge, mathematical content knowledge, positive behavior and respect, teacher enthusiasm (passion). The results of the CFA indicate that the constructs built have construct validity in the good category, convergent validity fulfilled because all AVE values are more than the minimum limit (0.5). Internal reliability (Cronbach's Alpha) = 0.96, Composite Reliability (CR) is in the range 0.88-0.92, and Average Variance Extracted (AVE) is in the range 0.55-0.58. The results of the CFA produced 27 items. Based on the measurement, it can say that the instrument of Holistic Assessment of Prospective Mathematics Teachers is suitable for use at the research.