The precision of electron beam lithography is analyzed using simulations of electron beam behavior in an electron optics, electron scattering behavior in a resist film on Si wafer, dissolution behavior of resist surface irradiated in the development process. Point spread functions because of the Coulomb repulsion of electrons in the optics, and scattering nature in the material are obtained. The placement accuracy is also determined by the analysis. This kind of simulations is so important that it should be continually improved to predict the precision of up-coming technologies in nanometer scale.