Battery unit mounting structure for vehicle

The present invention can provide a battery unit mounting structure for a vehicle which allows a drive battery unit and an air conditioning duct to be mounted on a floor panel of the vehicle in a manner that reduces cost, weight, and space, and also allows the floor panel to be reinforced. The battery unit mounting structure for a vehicle of the present invention includes a floor panel, a side member attached to a lower surface of the floor panel, and extending in a longitudinal direction of the vehicle, and a bracket mounted on an upper surface of the floor panel above the side member. The bracket includes an attachment portion which is attached to the side member in a three-layer structure, two vertical wall portions extending upward from respective corresponding end portions in a transverse direction of the vehicle of the attachment portion, and two support portions configured to support the battery unit, and each extending from an upper end of the corresponding one of the two vertical wall portions in a direction away from a center of the bracket.