A controller for a vehicle AC generator that allows the aging test time of a CMOS logic circuit to be reduced is provided. The controller includes a specified signal detecting circuit connected to a third external terminal to detect a specified signal, a voltage selector circuit that generates a voltage selector signal in response to the detection output of the specified signal detecting circuit, and a power supply circuit connected to the first external terminal to output, as internal power supply voltage, first power supply voltage in a first state in which the specified signal is not input to the third external terminal and second power supply voltage higher than the first power supply voltage in a second state in which the specified signal is input to the third external terminal.