The total length of starter harness 7 for exclusive use for connecting a starter for an engine and plus-side terminal 4a of in-vehicle battery 4 is increased by providing a surplus redundant segment 21 to increase resistance in harness 7 beyond length required for laying the harness in an engine room. Redundant segment 21 is collected in a form of rod by forming a two-fold portion by folding a portion of the single continuous harness 7, and further folding the two-fold portion twice, and fixed through harness holder 23 to bracket 22 of battery tray 25. Without using a resistor receiving limitation of the heat resistance, it is possible to suppress a voltage drop at the time of restart, problematical in a vehicle having an idle-stop function. A required resistance is obtained by increasing the length redundantly, so that a temperature increase of harness 7 is small.