Maintenance of Aluminium Cable Steel Reinforced (ACSR) relies on a life time management method, in which their replacement period is estimated by visual inspection and other means. It is difficult, however, to correctly estimate replacement period and prevent wire breaks by this method. After development of three types of devices to detect deterioration of hard-drawn aluminum stranded wires, hard-drawn copper stranded wires, and galvanized steel stranded wires, the demand is mounting for examining the detectability of deterioration of ACSR. To respond to this requirement, we successfully developed a device for detecting deterioration of ACSR.