Urban rail transit brings the benefits of various aspects of society. With the advent of fast and large trains, however, risk and scale of accidents have increased. Despite the fact that there is various safety features built into the modern metros, train faults happen from time to time. Especially, as urban railway vehicles in Korea have become deterioration rapidly, more advanced diagnosis methods are required to prevent various accidents. In this paper, we present diagnosis method for electrical wires to guarantee secure driving and authenticity more accurately in urban railway vehicles. Although there are kinds of conventional methods based on insulation resistance measurement and withstand test, it is extremely difficult to effectively diagnose obsolete equipments such as electrical wires and cables not new ones. This study is focused on development of diagnosis method and establishment of evaluation standard for electrical wires in urban railway vehicles.