An exposure system including a first laser light source, a second laser light source, a focusing module, an astigmatism generating element, and a photo detector, and an adjustment method thereof are provided. The first laser light source emits a first laser beam. The second laser light source emits a second laser beam. The focusing module includes a light converging unit disposed on transmission paths of the first laser beam and the second laser beam for projecting the first laser beam and the second laser beam onto a material. The material reflects at least a part of the first laser beam into a first reflective beam. The light converging unit and the astigmatism generating element are disposed on the transmission path of the first reflective beam. The photo detector is disposed on the transmission path of the first reflective beam from the astigmatism generating element.