1. An apparatus for correcting touch signal, comprising: a light emitting unit configured to emit at least one beam; a reflective element configured to reflect the at least one beam; a sensing unit configured to obtain a detective beam generated by reflecting the at least one beam by the reflective element, thereby generating a detective signal distribution graph, wherein the detective signal distribution graph indicates a plurality of pixel positions of an optical touching region and a plurality of corresponding signal intensities, and the reflective element is disposed at periphery of the optical touching region; and a control unit coupled to the light emitting unit and the sensing unit, and configured for: obtaining a plurality of intersections, at least one covered region and the pixel positions corresponding to each of the at least one covered region according to the detective signal distribution graph and the threshold value distribution graph, wherein each of the covered region corresponds to two adjacent intersections; calculating a first area occupied by each of the covered region according to the detective signal distribution graph and the plurality of intersections; determining whether an overexposure is occurred in the at least one covered region according to the first area corresponding to the at least one covered region; and correcting the at least one covered region being overexposed and the pixel position corresponding to the at least one covered region if the overexposure is occurred in the at least one covered region, wherein when the control unit obtaining the pixel position corresponding to each of the at least one covered region, the control unit is further configured for: obtaining a left border and a right border corresponding to each of the at least one covered region according to the detective signal distribution graph, wherein the left border and the right border pass through the two adjacent intersections corresponding to the at least one covered region, respectively; and setting a center between the left border and the right border as the pixel position corresponding to each of the at least one covered region, wherein when the control unit correcting the pixel position corresponding to the at least one covered region being overexposed, the control unit is further configured for: determining whether the overexposure is occurred in two adjacent covered regions among the at least one covered region; and calculating, if the overexposure is occurred in the two adjacent covered regions, a center between the left border of the at least one covered region at left and the right border of the at least one covered region at right among the two adjacent covered regions, and the center being served as a pixel position of the at least one covered region having the overexposure corrected.