The seesaw button of a heater control unit includes a guider formed with illumination holes corresponding to marking regions printed at the outer surface of a manipulation case with different colors, the guider being inserted into the manipulation case, a plurality of movable rods located at both sides of the guider to activate a contact switch of a substrate according to a manipulation of the manipulation casethe movable rods restoring the manipulation case to its original position when releasing the manipulation. The seesaw button further includes an accommodation housing that supports a middle portion of the guider coupled to the manipulation case, forms light inducing passages corresponding to the illumination holes and accommodates the movable rods and a plurality of prisms positioned at the light inducing passages that includes light emitted from light sources of the substrate toward the markings of the manipulation case.