LUMBAR SUPPORT DEVICE

A lumbar support device includes: a seat back frame; a warped plate supported by the seat back frame to press a back of a seated person; and a reinforcing plate that reinforces the warped plate, the reinforcing plate being able to curve together with the warped plate. The warped plate includes a holder that holds a first end portion of the reinforcing plate, and a non-interference portion that allows movement of the reinforcing plate relative to the warped plate.