A vehicle seat includes a seat component member that has a frame member, a cushion material, and a support member arranged on the frame member. The support member includes a frame-shaped member having a polygonal shape that can be attached to the frame member, and a bag-shaped planar member that is attached to the frame-shaped member in a tensioned state to support the cushion material. The frame-shaped member can be accommodated in the bag-shaped planner member while at least one side of the frame-shaped member is at a contracted state. The frame-shaped member is maintained at an expanded state as the at least one side of the frame-shaped member is at a non-contracted state, such that the planner member is expanded from an inner side thereof and is maintained at the tensioned state.