To analyze the effect of the crystal orientations and the grain size on the Young's modulus of thin polysilicon microelements, two-dimensional finite element models in plain strain condition were developed using a Voronoi structure. The number of grains in a model of a 10 μm square area was changed from 23 to 1200. The grain size and the crystal orientation of the film were analyzed by means of an electron back-scattering diffraction pattern (EBSP) method. The average grain size of the front surface of the thin film was about 0.69 μm, which is almost equal to the grain size of the Voronoi model having 300 grains. From the results of EBSP analysis, the specimen had no oriented structure. Therefore, random crystal orientation was given to each grain of the FEM models. When the number of grains increased, the Young's modulus converged on about 171 GPa and its scatter caused by the different sets of the random orientation was reduced. The Young's modulus obtained by the FEM analysis was larger than the value obtained by the tensile tests.