An electrical junction box having a novel structure in which a cover is externally fitted and assembled to a main body provided with a circuit board. The electrical junction box enables water that has entered the cover from reaching the circuit board via a micro-gap between the main body and the cover. At least one of an outer surface of a main body and an inner surface of a cover that oppose each other in a state in which the cover is assembled to the main body provided with a circuit board is provided with a guiding drain groove for guiding the water in the horizontal direction using capillary action.