An electrical connection structure includes a partition member provided with an opening, a casing, a plurality of connection members, and a mold. The partition member divides an inside of the casing into a first space and a second space. The plurality of connection members electrically connect a first electric circuit accommodated in the first space to a second electric circuit accommodated in the second space. The mold blocks the opening which penetrates the partition member. The partition member includes a first surface facing the first space, and a second surface that is reverse to the first surface and faces the second space. The plurality of connection members extend from the second space to the first space via the mold. A periphery of the surface of the mold that faces the second surface is in close contact with the second surface via a waterproof sealing member.