A control apparatus controls the generation of a vehicle electric generator having an armature winding, excitation winding and rectifier connected to the armature winding. The apparatus includes a flywheel diode connected to the excitation winding in parallel, a switch element connected to the excitation winding, a control signal setting circuit, and a signal output section. The setting circuit controls a duty ratio of the switch element in correspondence to a first generation status of the generator to control electric current flowing through the excitation winding while varying a switching frequency of the generator depending on a second generation status of the generator. The signal output section is connected to a junction point between the excitation winding and the switch element and outputs a signal, involving a duty ratio associated with the first generation status and a switching frequency associated with the second generation status, to an external device.