[en] A two-dimensional two-phase flow simulation code using the immiscible lattice-gas model is developed and parallelized on the vector-parallel super computer VPP500 and on the scalar parallel server AP3000. The user directive of VPP FORTRAN and the MPI library are used for parallelization on VPP500 and on AP3000, respectively. Reasonable efficiency of parallelization is obtained on VPP500 by procedure decomposition alone, since the band-width of node communication is very high. It is shown for AP3000 that not only procedure decomposition but also data decomposition is necessary because AP3000's bandwidth is much lower. MPI is found to be more effective than VPP FORTRAN for parallelization on AP3000. (author)