We have developed a hardware-in-the-loop simulation (HILS) system as a virtual running-test environment to replace actual test runs. It is essential for the vehicle model in the HILS system to run under real-time conditions and for actual vehicle motion to be simulated accurately. In this paper, we introduce the HILS model and report on the results of amplitude-frequency response tests executed on a rolling stock motion stand to improve the model's performance by modifying its parameters.