A regulator circuit includes: a regulator part configured to generate a constant internal power supply voltage based on an external power supply voltage; a connection port configured to receive power from the regulator part and to be connected to a connection cable having a predetermined cable resistance, the connection cable is configured to electrically connect the connection port to an external device; a current detecting part configured to detect a power supply current when the connection cable is connected to the connection port; and a voltage compensation part configured to compensate a voltage corresponding to a voltage drop due to the cable resistance according to a current value detected by the current detecting part.