The present invention improves heat dissipation of an electrical junction box. An electrical junction box includes a housing which houses a control circuit board disposed perpendicular to a power distribution board. The control circuit board includes a control circuit constructed on one side of an insulating substrate, electrical components mounted on the control circuit, and a heat dissipating means mounted on the other side. The power distribution board includes a plurality of bus bars laminated via a plurality of insulating layers. Consequently, heat generated by the electrical components can be dissipated efficiently by the heat dissipating means, thereby improving heat dissipation of the electrical junction box.