Disclosed are a battery diagnosis apparatus for a vehicle and a method thereof. The battery diagnosis apparatus for the vehicle includes a communication device that provides a communication interface with a plurality of vehicles, and a controller that collects vehicle state information and battery state information from the plurality of vehicles, manages a maximum voltage difference change rate of battery cells for each cumulative mileage with respect to the plurality of vehicles, and diagnoses abnormalities in batteries provided in the plurality of vehicles based on the maximum voltage difference change rate of the battery cells for each cumulative mileage.