A seat device includes a cushion portion configured to elastically support a seated person and a seat frame configured to support the cushion portion. The cushion portion includes a plurality of divided cushions divided in a seat width direction. The plurality of divided cushions each include a seat pad a seat cover that individually covers each seat pad, and a resin member that is engaged with at least one of the seat cover or the seat pad and is thus individually integrated with the seat pad covered by the seat cover. The resin member includes a snap-fit structure fixed to the seat frame by inserting from a seat front side to a seat back side.