A computer executable three-dimensional device simulation program product for the purpose of making a three-dimensional device simulation system which generates a three-dimensional model of a device by using a mask data performing the procedures of inputting cross-sectional feature information indicating a cross-sectional feature of an edge part of a mask, and calculating the three-dimensional model based on the mask data and input cross-sectional feature information, thereby enabling an easy generation of a complex three-dimensional feature by using pattern forming-use mask data when generating a three-dimensional feature model of a minute device.