For this study, a rigidity test car was designed and manufactured to enable investigation of how non-structural members in the carbody influence the rigidity and vibration characteristics of a commuter-type railway vehicle. Reinforcing beams and pillars designed for easy attachment and removal were installed on the ceiling, the side panels and the floor. The authors performed static load and excitation tests, and the results showed that the non-structural members, as well as the main (outer) body structures, affected the equivalent rigidity, natural frequencies, vibration shapes and response accelerations of the carbody.