A battery unit comprises a battery case, and a plurality of battery modules stored and held in the battery case. The battery case includes a bottom wall and a partition. The plurality of battery modules are mounted on the bottom wall. The partition is provided and erected on the bottom wall. The partition separates the battery modules adjacent in a second direction traversing a first direction. The first direction is oriented from a first end of the battery case at which an inlet is formed to a second end at which an outlet is formed. The partition extends along a plane where the battery modules face each other in the second direction along the battery modules. The partition is inclined in the extending direction.