To fill up a theoretical database necessary for the fusion reactor development program a plasma simulator METIS was designed and a prototype plasma simulator ProtoMETIS was constructed. METIS is projected on the basis of a MIMD type parallel computer composed of 250 processor elements with distributed memories and optimized for analyses of the nonlinear MHD behavior of a plasma and the loss of alpha particles due to magnetic field ripples in a tokamak. By using ProtoMETIS performance of the METIS architecture was investigated for the above problems and satisfactory results were attained. It was also confirmed that a simulation of a free electron laser used for plasma heating and an MHD equilibrium computation of a tokamak plasma were carried out efficiently on the plasma simulator.