A laser annealing apparatus for sequential lateral solidification (SLS) to uniformly crystallize silicon on an entire silicon substrate by minimizing the dislocation of the silicon substrate during laser beam irradiation is disclosed. During the laser annealing, a vacuum chuck holds the silicon substrate on a movable stage. The device includes a laser source, an optical system patterning the shape and energy of a laser beam irradiated from the laser source, a vacuum chuck supporting a silicon substrate, and a movable stage supporting the vacuum chuck as well as transferring the vacuum chuck in a predetermined direction. Accordingly, the apparatus improves the degree of crystallization because it is able to uniformly carry out SLS on an entire surface of the silicon substrate.