A parameter extracting method capable of accurately and effectively extracting parameters used for charged particle beam exposure. The method comprises the steps of forming an unknown parameter layer on a known parameter layer, forming a resist on the unknown parameter layer, subjecting the resist to exposure through patterns changed in an existing range, and extracting parameters of the unknown parameter layer using the exposure result. In the parameter extraction method, parameters of layers lower than the unknown parameter layer are known. Therefore, layer combinations to be considered and the number of experimental data can be drastically reduced. After parameter extraction of the unknown parameter layer, an unknown parameter layer is newly formed on the layer. Then, the parameter thereof is extracted in the same manner. Thus, the parameter is extracted sequentially from lower layers and therefore, the parameter in the multitiered structure having various layer combinations can be accurately and effectively extracted.