In order to grow a high quality SiC bulk single crystal, it is important to moderate the residual stress in the grown crystal. The residual stress is affected by not only the temperature distribution, but also by the boundary conditions. In this study,, firstly, the effect of the polycrystal and of the crucible walls on the stress distribution was numerically analyzed. The effect of the grown crystal shape on the residual stress was also analyzed and compared to the growth experiment. It is pointed out that in order to moderate the residual stress, it is necessary to take care not only of the temperature distribution but also of the boundary conditions.