When shock impinges on the bow shock ahead of a blunt body, the shock-shock interaction occurs. Such interactions are classified into six patterns by Edney. In the present research we selected an interaction referred to as Type IV, where the impinging shock was generated by another blunt body.It is well known that pressure and heat transfer are greatly increased at the impinging point. We measured the pressure distributions along the body surface where shock impinges.Then, we performed numerical simulations to investigate the heat transfer rate and the interaction pattern, though it is two-dimensional for simplicity. We employed the FVS, Flux Vector Splitting, method to solve the Navier-Stokes equations. From the numerical simulations, the clear interaction pattern was obtained and it was found that this pattern is an unstable phenomenon.