HEAD REST POSITION ADJUSTMENT DEVICE

To adjust the position of a headrest accurately regardless of how long or how short the distance between a head and the headrest is, a headrest position adjustment device 100 includes a capacitance sensor unit 10, and a drive motor unit 30. The capacitance sensor unit 10 includes a plurality of electrode groups 11 to 15 each configured by a plurality of sensing electrodes 11A to 15A and 11 B to 15B. The total electrode area of each of the electrode groups 11 to 15 is switchable by a switching unit 22 of a circuit unit 20 between at least a total electrode area A and a total electrode area A+B. The total electrode area A is selected when the distance d between a head 49 and a headrest 43 is short, and the total electrode area A+B is selected when the distance is long. In this way, the sensitivity is changed depending on how long or how short the distance is. An estimated center position of the head 49 is calculated based on capacitance values obtained, and thereby the position of the headrest 43 is adjusted.