Method and apparatus for diagnosing driving operation

An apparatus is provided for providing users diagnosis on driving operations in the same manner as diagnosing vehicle failures and for presenting evaluation with supporting data so that users may recognize their driving operations. The apparatus reads out driving data for a plurality of driving cycles from an electronic control unit on board the vehicle. The electronic control unit includes a memory for storing driving data representing fuel efficiency condition of the vehicle in accordance with driving operation by a user in each driving cycle of the vehicle. Charts are produced representing fuel efficiency condition for each driving operation by the user for each driving cycle, based on the read out driving data. The charts are output as comparison results for each one of the driving cycles.