A method for generating backscattering intensity with which charged particles are backscattered to a resist layer when charged particle beam is irradiated onto the resist layer which is formed on plural layers, each of which includes a pattern of one substance or a plurality of substances. For the n.sup.th layer from the resist layer among the plural layers, there is provided, for each of the substances in the n.sup.th layer, a reflection coefficient rn, which corresponds with the number of particles reflected by the n.sup.th layer; a transmission coefficient tn, which corresponds with the number of particles transmitted by the n.sup.th layer; and a scatter distribution in which the charged particles are scattered within the n.sup.th layer. The generation method comprises a first step of generating the backscattering intensity by using the reflection coefficient rn, the transmission coefficient tn, and the scatter distribution.