A seat cushion is provided. The seat cushion includes an upper pad, a lower pad, a support structure, a plurality of optical modules, and a processor. The upper pad includes a plurality of transparent areas. The lower pad is provided with a plurality of grooves to accommodate the optical modules. The support structure is connected between the upper pad and the lower pad. The optical modules are located below the upper pad and are disposed corresponding to the transparent areas. The optical modules respectively transmit sense signals and respectively receive feedback signals corresponding to the sense signals. The processor is coupled to the optical modules and is configured to collect optical signals.