Instead of a relay block which is present in bus bar circuits in a conventional electric junction box, semiconductor switching devices 14 are provided, and a power distributing unit PD which is independent of a bus bar circuit unit JB is structured by concentrating these semiconductor switching devices 14, output terminals 12 of this power distributing unit PD being connected to appropriate bus bars 32 of the bus bar circuit unit JB. The power distributing unit PD and the bus bar circuit unit JB are incorporated in a common housing 40.