Random vibration is popular that its characteristic is close to that of actual envionmental condition. However, presentation of practical use according to engine installed parts are a few, and its usage is unknown. Therefore, we investigated how to set condition of random vibration testing. As a result, the conversion formula of dimensions for random vibration testing was got. Then, random vibration test whose condition was set by this formula, was more repuroducible about characteristic change as wear of mechatronics parts for automobiles than that by sine-wave vibration.