An overlap mark set is provided to have at least a first and a second overlap marks both of which are located at the same pattern layer. The first overlap mark includes at least two sets of X-directional linear patterns, having a preset offset a1 therebetween; and at least two sets of Y-directional linear patterns, having the preset offset a1 therebetween. The second overlap mark includes at least two sets of X-directional linear patterns, having a preset offset b1 therebetween; and at least two sets of Y-directional linear patterns, having the preset offset b1 therebetween. The preset offsets a1 and b1 are not equal.