An IC regulator for controlling an alternator by changing contents of control in dependence on ambient temperature includes a control voltage limiter (2), a field current controller (3), a temperature sensor (4), a first comparator (5) for comparing the ambient temperature (T) with an activation temperature (TP1) and a reset temperature (TS1), and a second comparator (6) for comparing the ambient temperature (T) with a second activation temperature (TP2). The first comparator (5) outputs a limiter control signal (C2) when the ambient temperature (T) exceeds the first activation temperature (TP1) while resetting the limiter control when the temperature (T) becomes lower than the first reset temperature (TS1). The second comparator (6) outputs a field current interrupt signal (C3) when the ambient temperature (T) exceeds a second activation temperature (TP2) while resetting the signal (C3) when the temperature (T) becomes lower than the second activation temperature (TP2).