Three-dimensional shock wave/turbulent boundary layer interaction region induced by a blunt protuberance is experimentally investigated. Experiments are performed under the testing condition of freestream Mach number of 2, 3 and 4 with almost adiabatic wall condition. The primary separation lines locate almost same position irrespective of freestream Mach number, and freestream Mach number independence on the primary separation region is revealed. However, detailed flow structures for each Mach number are different. Pressure begins to rise at slightly ahead of the primary separation line where stream lines begin to deflect outward. As freestream Mach number is increased, the maximum pressure becomes higher but locations, where the pressure begins to rise and reaches to its maximum level, exist at almost same locations respectively regardless of freestream Mach numbers. The oscillating separated shock waves are observed in the interaction region by instantaneous shadow graph technique and significant unsteady flow structure is captured.