A wire harness unit including: a conduction path that conducts electricity between in-vehicle devices; and a cooling tube that cools the conduction path, wherein: the conduction path has a hollow tubular conductor having conductivity, the cooling tube is more flexible than the tubular conductor and is separate from the tubular conductor, the cooling tube is connected to an end of the tubular conductor, and the tubular conductor and the cooling tube are configured to circulate a cooling medium therethrough.