When a battery case (24) housing a plurality of batteries (42) is mounted on the vehicle body frame (11) that includes a cross member (20) extending in a vehicle width direction, the cross member (20) of the vehicle body frame (11) is disposed within the recess portion (39b), extending in the vehicle width direction, that is formed in the battery case (24), and therefore, it is possible to mount the battery case (24) while avoiding interference with the cross member (20). Although the intermediate part in the fore-and-aft direction of the battery case (24) housing heavy batteries (42) is susceptible to downward deformation, it is possible to prevent deformation of the battery case (24) by fixing the recess portion (39b) of the battery case (24) to the cross member (20) by fixing means (54).