Utilizing NAL middle scale shock tunnel and RCS (Reaction Control Subsystem) experimental gas mixing system, diagnosis of air condensation of hypersonic flow by Pitot pressure wave form was attempted. By using dry air and moist air as working gases for low pressure pipe of shock wind tunnel, the change of Pitot pressure wave form to air condensation and the onset point were investigated, varying stagnation pressure of the wind tunnel, temperature of uniform flow and moisture content. From these results, it was clarified that the diagnosis in case of using dry air and changing static temperature of uniform flow at the measuring point was almost the same as the test results by Daum et al. Further, it was found that the air flow diagnosis can be made with comparatively good accuracy by simple measurement of Pitot pressure wave form, and condensation can also occur even in the safety side from onset point as shown by Daum et al. depending on the moisture content of working gas.