The present disclosure improves heat dissipation performance. An electrical junction box (A) includes: a box main body (10) constructed by assembling a side wall member (14) to an outer surface of a base member (13); and a busbar (12) housed in a busbar housing chamber (44) of the side wall member (14), and a heat dissipation space (72) that brings the busbar housing chamber (44) into communication with the outside of the box main body (10) is formed between the base member (13) and the side wall member (14). Heat in the busbar housing chamber (44) passes through the heat dissipation space (72) and is thus dissipated to the outside of the box main body (10).