The responses of a cabinet for a reactor protection system under seismic loadings are analysed by using the finite-element method, and its dynamic characteristics are evaluated. Analysed modes are compared with the measured data from a resonance search test. The structural safety of the cabinet is evaluated considering the required response spectrums of the operation-base and safe-shutdown earthquakes. The transient response of the cabinet is analysed by utilizing the measured acceleration of the vibration table representing the seismic motion of the ground. Time histories of accelerations at the locations of major internal parts are extracted. The transient responses are compared with those from the seismic test and the results were found to closely represent the system.