To enable connection of a power-distribution cable and a DC plug socket by a simple operation without mixing up cable polarities.

A power-distribution cable 30 includes a plurality of conductors 31 of different polarities covered with a protective coating 34. To supply DC power to the DC plug socket 1, the ends of the conductors 31 are exposed out of the protective coating 34 and connected to the DC plug socket 1. The lengths of the exposed conductors 31 without the protective coating 34 are different.