Adjusting Device of Front and Rear Positions of Seat

In an arrangement which includes: a seat support body slidably supported on a fixed rail fixed to a floor; a power supply device supplying power to an electrical component on a seat side; and a drive device driving the seat support body in a front-and-rear direction and having a motor and a transmission member disposed so as to pass longitudinally through an interior of the fixed rail, the power supply device includes: a housing an electric wire for power supply; and a slider linked to the seat support body and slidable within the fixed rail. The electric wire is drawn out from the housing, retained by the slider and slidable within the fixed rail. The slider has an interference-avoiding portion for avoiding interference with the transmission member disposed so as to pass longitudinally through the interior of the fixed rail. Accordingly, the transmission member of the drive device and the slider for retaining the electric wire, which slides within the fixed rail, can be arranged in proximity to each other within the fixed rail while avoiding interference therebetween, thus enabling simplification and a reduction in the size of a rail structure.