There can be performed the best power-generation control without enlarging the apparatus, deteriorating the reliability, and raising the cost. The power-generation control apparatus is provided with a power-generation amount suppression determination unit that determines whether or not to change a power-generation amount suppression level for suppressing the power-generation amount of the in-vehicle electric rotating machine, based on a present generation-voltage command value generated by a generated-voltage command unit and a generated-voltage past command value based on a past generated-voltage command value stored in a generated-voltage command storage unit, and that determines whether or not the power-generation amount suppression control is required, based on at least one of a past value and a present value of the generated-voltage command; therefore, there can be performed the best power-generation control without enlarging the apparatus, deteriorating the reliability, and raising the cost.