Disclosed is a chair seat board (100) and a chair (1000) to which a chair backboard (200) is coupled. The chair seat board (100) may comprise: a frame unit 40 having a plurality of frames (41, 42, 43, 44) configured in a hollow shape, respectively, and implemented to allow independent movement; and a support unit configured to support the frame unit 40 while being coupled to the frame unit (40) on a lower side of the frame unit (40).