Circuit assembly and electrical junction box

A circuit assembly includes: a substrate with an electrically conducting path; plate-shaped busbars that have connection portions connected to the electrically conducting path of the substrate, and are arranged in an orientation in which plate surfaces thereof intersects with a surface of the substrate; a heat discharge member that is laid on a side of the substrate opposite to the busbars, and is configured to discharge heat of the substrate; and a resin frame that extends along the busbars, and holds the busbars while being in intimate contact with the busbars, wherein the frame includes mounting portions mounted on at least either the substrate or the heat discharge member.