POWER SUPPLY DEVICE

A technology disclosed in the present specification is a power supply device configured to supply electric power to a seat S that can slide and rotate with respect to a floor part F of a vehicle. The power supply device comprises: a power transmission unit that is provided on the floor part F and extends along a sliding direction in which the seat S slides; and a power reception unit that is provided on the seat S and receives electric power from the power transmission unit in a contactless manner, wherein the power transmission unit is provided such that the length dimension in the sliding direction is longer than the length dimension in a direction orthogonal to the sliding direction, and a portion of the power reception unit , which receives electric power from the power transmission unit , is disposed within an installation range of the power transmission unit in a state of being close to the power transmission unit while the seat S is sliding and rotating.