Headrest position adjustment method and device

A headrest position adjustment device (100) is provided with: a capacitance sensor unit (10) that comprises a plurality of sensing electrodes (11-15); and a control unit (30) that controls the drive of a drive motor (44) on the basis of a detection result from the capacitance sensor unit (10). The control unit (30) calculates a head position (P) of a head (49a) from a sensor output in an arithmetic processing circuit (28), and moves a headrest (43) such that the head position (P) falls within a proper region (PS) demarcated by preset predetermined distance from the headrest (43) and predetermined range in the height direction of the headrest (43). During a position adjustment operation in which a center position (43P) of the headrest (43) is being moved to a target adjustment position for the head (49a), processing of recalculating the target adjustment position is performed, and the position adjustment operation of the headrest is changed according to the result of the calculation.