The electrical junction box has a case, which accommodates a printed circuit board provided in a lower side of the case. The case also receives an electrical wiring circuit and a busbar circuit disposed in an upper side of the case so as to be parallel to the printed circuit board. Wiring harness connectors are mounted on a side wall of the case, and relay connectors are positioned on the side wall or another side wall of the case. The side walls are perpendicular to the printed circuit board. The wiring harness connectors are connected to inner circuits including the printed circuit, the busbar circuit, and the electrical wiring circuit. The case has a top cover, a bottom cover, and a horizontal intermediate partition. The intermediate partition is provided with the electrical wire circuit on an under surface of the partition so as to be opposed to the printed circuit. The upper surface of the intermediate partition is provided with the busbar circuit.