The vehicle-use battery monitor apparatus includes a first function of receiving a power generation rate indicative of an operating state of a vehicle alternator from a power generation control device, a second function of detecting a charge/discharge current of a vehicle battery, a third function of transmitting the power generation rate to an electronic control unit for controlling an output power of a vehicle engine in order that an idle-up control is performed depending on a value of the power generation rate, a fourth function of increasing the value of the power generation rate when it is determined that the vehicle battery is in a discharge state on the basis of a detection result by the second function, and a fifth function of generating a notification signal in accordance with which an indicator light makes an indication of the power generation rate being increased by the forth function.