In crystallization of a silicon film by annealing using a linear-shaped laser beam having a width of the short axis of the beam is ununiform, the profile (intensity distribution) of the laser beam is evaluated and the results are fed back to a condition of oscillating the laser beam or an optical condition for projecting the laser beam onto the silicon film, whereby a display device comprising a high-quality crystalline silicon film is manufactured. The energy distribution of the linear-shaped laser beam is determined by a detector type CCD camera which is moved stepwise in the directions in which its long axis and short axis extend, respectively, and a value obtained by dividing an accumulated intensity E in the long axis direction obtained by accumulating the detected signal in the direction parallel to the short axis by the square root of the width W of the short axis of the above linear-shaped laser beam in each position of the long axis: E/√{square root over ( )}(W), is determined in all the positions of a cross section of the linear-shaped laser beam to evaluate the above intensity distribution.