In a case of a power distribution branch unit used in a vehicle or the like, one end of a branch wiring is connected to an exposed part of a main covered cable (a part where a core wire is exposed without an insulation cover). Branch couplers are connected to the other ends of the branch wiring and fixed to the case so as to be exposed to an outside. At least one retainer is disposed inside a hole part that is formed in the case and fixes the main covered cable.