An apparatus for controlling generation of power in vehicles which include an engine associated to a generator having a field winding and a battery, comprising: a voltage comparing section (207, 208, 204, 206) that compares either output voltage of the generator or terminal voltage of the battery with a predetermined regulation voltage; a field current controlling section that controls field current passing through the field winding of the generator; a field current suppressing section (203, 205, 213) that drives the field current controlling section based on a comparison result of the voltage comparing section (207, 208, 204, 206) to suppress the field current, and gradually increases the field current or restricts the maximum value of the field current; and an external output terminal, which is a communication terminal that is connected to an external control unit which is disposed outside the generator and the apparatus, that transmits either a first signal outputted from the voltage comparing section (207, 208, 204, 206) and inputted into the field current suppressing section (203, 205, 213) or a second signal corresponding to the first signal, the first signal or the second signal, which is obtained by comparing the output voltage of the generator with the regulation voltage before the control is performed, is transmitted to the external output terminal without going through the field current suppressing section (203, 205, 213), such as the external control unit can perform control of idling engine speed in response to applied electrical load to stabilize the idling engine speed, characterized in that the field current suppressing section (203, 205, 213) comprises a field current suppressing circuit which detects a voltage at a connection point between the field current controlling section and the field winding, and in that the apparatus further comprises a signal equalizing section that equalizes the first or second signal, wherein the signal equalizing section performs equalization for a period of time longer than a control period of ignition of the vehicle, such as the influence of ignition noise generated during idling can be eliminated, thereby allowing the operation state of the generator to be more accurately detected and allowing the idling engine speed to be more stable. a voltage comparing section (207, 208, 204, 206) that compares either output voltage of the generator or terminal voltage of the battery with a predetermined regulation voltage; a field current controlling section that controls field current passing through the field winding of the generator; a field current suppressing section (203, 205, 213) that drives the field current controlling section based on a comparison result of the voltage comparing section (207, 208, 204, 206) to suppress the field current, and gradually increases the field current or restricts the maximum value of the field current; and an external output terminal, which is a communication terminal that is connected to an external control unit which is disposed outside the generator and the apparatus, that transmits either a first signal outputted from the voltage comparing section (207, 208, 204, 206) and inputted into the field current suppressing section (203, 205, 213) or a second signal corresponding to the first signal, the first signal or the second signal, which is obtained by comparing the output voltage of the generator with the regulation voltage before the control is performed, is transmitted to the external output terminal without going through the field current suppressing section (203, 205, 213), such as the external control unit can perform control of idling engine speed in response to applied electrical load to stabilize the idling engine speed,