The present invention relates to a fabrication method for polycrystalline silicon thin film in which amorphous silicon is crystallized by laser using a mask having a mixed structure of laser transmission pattern group and laser non-transmission pattern group, wherein the mask comprises two or more of dot pattern groups in which the non-transmission pattern group is perpendicular to a scan directional axis, and the dot pattern groups are formed in a certain shape and comprise first non-transmission patterns that are not respectively arranged in a row in an axis direction perpendicular to the scan directional axis, and second non-transmission patterns that are formed in the same arrangement as the first non-transmission patterns, but are positioned in such a manner that the second non-transmission patterns are parallel to the first non-transmission patterns and vertical axis of the scan directional axis.