In a current detection device for detecting current in a busbar, a reduction in device size may be realized by employing a small magnetic core. The prevention or reduction of excessive heat generation by the busbar, the facilitation of the attachment task, and a reduction in the amount of space required for the attachment task may also be realized. The folded-back busbar is U-shaped with a bar-shaped penetration portion that passes through a hole portion of a magnetic core, two bar-shaped extension portions, and two flat plate-shaped penetration portions. The width of each terminal portion is larger than the widths of the penetration portion and the extension portions. An insulating casing supports the magnetic core, a Hall element, and the folded-back busbar in a fixed positional relationship, with the two terminal portions being exposed to the outside.