To provide a battery unit for a working vehicle capable of securing necessary rigidity for lamination with a simple structure and of efficient cooling matching a housing space.

The battery unit for the working vehicle includes a plurality of batteries, a plurality of battery cases each in a bottomed box shape and housing the battery with its terminal topside, and spanning plates 4 to 6 provided on respective battery cases and spanning between opposed sidewalls of the respective battery cases. The spanning plates 4 to 6 are freely selected from a plurality of spanning plates each having different thickness dimension, and are attached to the respective battery cases, and the respective battery cases are placed on the spanning plates 4 to 6 and laminated in the vertical direction.