A vehicle AC generator apparatus includes one or more rectifier elements for rectifying a generated AC voltage, and a generator control apparatus which monitors the voltage difference between opposing terminals of a rectifier element, to thereby detect the commencement of electrical generation upon engine starting as the time point at which the polarity of the voltage difference first corresponds to the forward conduction direction of the rectifier element. Controlled parameters such as the current supplied to a charging warning lamp and the excitation current of a generator winding are changed appropriately when generation commencement is detected.