An in-vehicle charge control system includes a vehicle-state detector that detects a running state of a vehicle, a battery-state detector that detects a charge level of an in-vehicle battery, a fuel-efficiency-enhancement controller that predicts a discharge amount to be discharged by the battery under a discharge condition, sets a lower limit of the battery charge level on the basis of the battery charge level detected by the detector such that the lower limit of the battery charge level is higher than a battery charge level at which the battery begins to degrade by the predicted discharge amount, and controls a power generation amount of a vehicle generator according to the vehicle state detected by the detector. The system with this configuration can maintain the battery charge level and enhance the fuel efficiency simultaneously under practical use conditions.