a method of manufacturing a poly - crystalline silicon film includes the steps in which an excimer laser anneals an amorphous silicon film deposited on a glass substrate and makes the same into the poly - crystalline silicon while the glass substrate is moved in a moving direction relative to the laser . prior to carrying out the annealing step , a couple of the laser pulses are applied to different places of the a - si film , provided that each of the laser pulses has different energy fluence and one pulse at a time is applied to the a - si film . the pulse applied area is divided into two sections by a reference line perpendicular to the moving direction of the glass substrate . average grain sizes of the p - si film in the two sections are compared to each other to determine the moving direction .