In the discrete element method analysis, the number of particle elements affects the calculation time. Because of this disadvantage, a method called coarse-grained method is sometimes used to improve the calculation speed by replacing multiple particle elements as a single particle element. In this study, a contact force model based on Hertzian contact theory is implemented in a contact force calculation between coarse-grained elements, and the contact force is used as input force for vibration analysis of a ball mill. Compared to the analysis results obtained by the conventional coarse-graining method using a contact force model based on linear springs, the proposed contact force calculated by the proposed mode closes the one of the original model.