Apparatus for diagnosing a battery of a vehicle and method thereof

Disclosed are an apparatus and method for diagnosing a battery of a vehicle. The apparatus includes storage that stores a threshold value for each accumulated driving distance section corresponding to a state of the vehicle, and a controller that collects vehicle state information and battery state information from a plurality of vehicles, determines a maximum voltage difference change rate of a battery cell for an accumulated driving distance for each vehicle, and diagnoses an abnormality in a battery provided in each vehicle based on the maximum voltage difference change rate of the battery cell for the accumulated driving distance of each vehicle and a threshold value corresponding to the maximum voltage difference change rate.