Hypersonic vehicles experience high speed and high temperature flow environment. At the time, Shock-wave/boundary layer interaction can occur which leads to local peaks of heat transfer. Therefore ablation phenomenon can occur at the interaction region. To understand the ablation phenomenon by the interaction, numerical investigation is performed considering shock-wave on boundary layer of a flat plate consisting of carbon/carbon. The coupled scheme with thermochemical ablation model is used with the higher-order overset grid method to conveniently reflect changing shapes by ablation. By the numerical approach, ablation process at flat plate by Shock-wave/boundary layer interaction during 0.0s to 4.12 s is discussed.