To provide an electrical junction box which can avoid abnormal sound caused by loosening between a box main part and a lower cover.

This electrical junction box 11 comprises a lower cover 12 and a box main part 13. A flange 16 with an arcuate cross-section with a constant curvature is formed on an outer circumference of an upper end of the lower cover 12. Coupling parts 14 are provided near points A1 of the flange 16. Coupling protrusions 15 are formed on the box main part 13. Differences between points A2 and A3 and the point A1 are predetermined so as to be equal to, or a little larger than, a design clearance between the coupling part 14 and the coupling protrusion 15. When the lower cover 12 and the box main part 13 are coupled with each other, the coupling parts 14 and the coupling protrusions 15 are engaged with each other to fix the lower cover 12 to the box main part 13.