A simulation-based evaluation and analysis support system called SEAMAID has been developed for man-machine interface design in the domain of nuclear power plant. The SEAMAID can simulate the interaction between operators and human-machine interface (HMI), and then support the analyst to evaluate the HMI by using the simulation results. A case study of the evaluation was conducted for conventional type of central control room design of an nuclear power plant, in order to demonstrate the effectiveness of the SEAMAID for the improvement of HMI designing from various human factors viewpoints.