A steering wheel heater device comprising: a plurality of steering wheel heaters each configured of an electrical resistor which produces heat by electrical energy, each of the plurality of steering wheel heaters having a first terminal and a second terminal and being included in a steering wheel; a plurality of first inductors (Lb) each connected in series to the first terminal of each of the plurality of steering wheel heaters; at least one switch (101; 102) for turning on and off supply of power to the plurality of steering wheel heaters; and a sensor circuit electrically connected to the first terminals of the plurality of steering wheel heaters and to the plurality of first inductors (Lb), for determining whether a detected subject is in contact with the plurality of steering wheel heaters, based on a magnitude of capacitance of each of the plurality of steering wheel heaters, wherein the at least one switch is at least one of a first switch connected in series via the plurality of first inductors (Lb) to the first terminal of each of the plurality of steering wheel heaters and a second switch connected in series to the second terminal of each of the plurality of steering wheel heaters, and the steering wheel heater device further comprises a controller for determining valid periods in each of which the sensor circuit determines whether the detected subject is in contact with respective one of the plurality of steering wheel heaters, and for disabling the sensor circuit during periods other than the valid periods, the valid periods synchronizing with an on-state and an off-state of the supply of power to each of the plurality of steering wheel heaters, and the controller enables the sensor circuit while switching between the plurality of steering wheel heaters in a time-sharing manner. a plurality of steering wheel heaters each configured of an electrical resistor which produces heat by electrical energy, each of the plurality of steering wheel heaters having a first terminal and a second terminal and being included in a steering wheel; a plurality of first inductors (Lb) each connected in series to the first terminal of each of the plurality of steering wheel heaters; at least one switch (101; 102) for turning on and off supply of power to the plurality of steering wheel heaters; and a sensor circuit electrically connected to the first terminals of the plurality of steering wheel heaters and to the plurality of first inductors (Lb), for determining whether a detected subject is in contact with the plurality of steering wheel heaters, based on a magnitude of capacitance of each of the plurality of steering wheel heaters, wherein the at least one switch is at least one of a first switch connected in series via the plurality of first inductors (Lb) to the first terminal of each of the plurality of steering wheel heaters and a second switch connected in series to the second terminal of each of the plurality of steering wheel heaters, and the steering wheel heater device further comprises a controller for determining valid periods in each of which the sensor circuit determines whether the detected subject is in contact with respective one of the plurality of steering wheel heaters, and for disabling the sensor circuit during periods other than the valid periods, the valid periods synchronizing with an on-state and an off-state of the supply of power to each of the plurality of steering wheel heaters, and the controller enables the sensor circuit while switching between the plurality of steering wheel heaters in a time-sharing manner.