ON-VEHICLE COMMUNICATION DEVICE

To provide an on-vehicle communication device which can maximally write data into an electronic control device (hereafter called as ECU) of a vehicle from a vehicle external communication device within a range not causing the exhaustion of a battery remaining quantity.SOLUTION: An on-vehicle communication device which can communicate with a vehicle external communication device and at least one ECU which is mounted to a vehicle calculates a prediction power amount P being a prediction value of a power amount of the vehicle necessary for writing write-in objective data from the vehicle external communication device into a write-in objective ECU via the on-vehicle communication device in S160. When it is determined that a battery remaining amount is larger than the prediction power amount P in S180, the on-vehicle communication device transfers the write-in objective data to the write-in objective ECU from the vehicle external communication device in S190, however, when it is determined that the battery remaining amount is not larger than the prediction power amount P in S180, does not transfer the write-in objective data.SELECTED DRAWING: Figure 2 【課題】車外通信装置から車両の電子制御装置（以下、ＥＣＵ）へのデータ書き込みが、バッテリ残量の枯渇を招かない範囲で、できるだけ実施されるようにすることができる、車載通信装置を提供する。【解決手段】車外通信装置と、車両に搭載された少なくとも１つのＥＣＵとの、各々と通信可能な車載通信装置は、車外通信装置からの書込対象データが当該車載通信装置を経由して書込対象ＥＣＵに書き込まれるのに必要な、車両における電力量の予測値である予測電力量Ｐを、Ｓ１６０で算出し、Ｓ１８０にて、バッテリ残量が予測電力量Ｐよりも大きいと判定した場合には、Ｓ１９０にて、車外通信装置から書込対象ＥＣＵへの書込対象データの転送を実施するが、Ｓ１８０にて、バッテリ残量が予測電力量Ｐよりも大きくないと判定した場合には、書込対象データの転送を実施しない。【選択図】図２