An electrical junction box that prevents deformation of a casing and breakage of a printed board due to an inserting force of a connector or the like is provided. A printed board is contained in a lower casing member. A bus bar laminated element is contained in the lower casing member above the printed board. An electrical component containing section including juxtaposed connector containing portions is provided on an upper side of an upper casing member above the bus bar laminated element. The upper casing member is mounted on the lower casing member. An upper reinforcement rib extends down from a lowermost stage insulation plate in the bus bar laminated element at a location below the electrical component containing section. The upper reinforcement rib is inserted into a through-hole in the printed board to extend down toward a bottom surface of the lower casing member. A lower reinforcement rib extends up from the bottom surface of the lower casing member to oppose the upper reinforcement rib. The upper and lower reinforcement ribs contact each other.