The main purpose of this study was to develop a scale for measuring content knowledge (CK) and pedagogy content knowledge (PCK) of in-service elementary teachers on mathematical fractions. Another aim of this study was to consider whether CK and PCK are separate from each other, or are in a single body. Therefore, a scale containing 22 items about mathematics fractions was designed and administered to 256 elementary teachers. Exploratory factor analysis indicated four factors that three of which are included in PCK, that is, instruction, task, and student, whereas CK had just one factor. Also to evaluate fitness of model, confirmatory factor analysis was used. The results revealed that CK and PCK are separate and correlated, and the scale has suitable validity and reliability to measure CK and PCK of in-service elementary teachers on mathematics fractions.