In order to estimate the wind tunnel data uncertainty, it is necessary to consider the error propagation caused by the tunnel flow quality. At the NAL 1.27 m hypersonic wind tunnel, multi point calibration tests of the flow field and 6-component force tests of a winged vehicle model were conducted to estimate uncertainties of aerodynamic coefficients. A statistical assessment of Mach number distributions in the uniform core flow gave us an uncertainty of dynamic pressure. Contributions of each uncertainty to the result uncertainties were examined and the large contributions of the dynamic pressure uncertainty were found. These estimated uncertainties were validated by repeat test results and comparisons of the same model test results obtained in another wind tunnel at the same test condition. This uncertainty estimation method is appropriate for hypersonic wind tunnel testing since the model existence gives little effect on the upstream flow.