Pressure-induced structural transformation in cubic silicon carbide is studied with the isothermal-isobaric molecular-dynamics method using a new interatomic potential scheme. The reversible transformation between the fourfold coordinated zinc-blende structure and the sixfold coordinated rocksalt structure is successfully reproduced by the interatomic potentials. The calculated volume change at the transition and hysteresis are in good agreement with experimental data. The atomistic mechanisms of the structural transformation involve a cubic-to-monoclinic unit-cell transformation and a relative shift of Si and C sublattices in the 100 direction.