The purposes of this study were to develop a model to measure the belief in Buddhism of junior high school students at Chiang Rai Buddhist Scripture School, and to determine construct validity of the model for measuring the belief in Buddhism by using Multitrait-Multimethod analysis. The samples were 590 junior high school students at Buddhist Scripture School who selected using the multi-stage random sampling. Three-Choice Situational Buddhist Belief Test (Sbbd) and Five-Scale Buddhist Belief Test (Rbbd) were used for data collection. Data were analyzed by descriptive statistics, CFA, and MTMM. The findings showed that 1) the results of the second order confirmatory factor analysis for measuring the belief in Buddhism were correlated with the empirical data at a good level (Sbbd: X[superscript 2]/df = 1.141, p-value = 0.146 and Rbbd: X[superscript 2]/df = 1.071, p-value = 0.287), and 2) multitrait-multimethod analysis had construct validity at a good level (X[superscript 2] = 33.664, df = 26, p-value = 0.144, CFI = 0.999, TLI = 0.998, RMSEA = 0.022, SRMR = 0.032, X[superscript 2]/df = 1.294). Both types of tests used for measuring the belief in Buddhism had convergent validity at a high level, discriminative validity at a moderate level, and reliability at a high level.