An electrical junction box is provided to reduce looseness of a cover. The electrical junction box includes a box body and the cover to be slidably mounted on a lateral side of the box body from above. The cover has a front wall and a pair of left and right sidewalls connected to both left and right ends of the front wall to overlap with left and right connecting walls of the box body, providing a U-shaped cross section. The electrical junction box further includes first slide guides provided on both of the cover and the box body and second slide guides provided on both of the cover and the box body. The second slide guides are positioned in areas where the left and right sidewalls of the cover overlapping with the left and right connecting walls of the box body. Further, the second slide guides are closer to the front wall of the cover being mounted to the box body than the first slide guides.