Distinct element method (DEM) proposed by Cundal and Strack is useful for simulating behavior of particle beds. However, the results of the simulation differ from the experiment in general Although the rolling friction should be taken into account, it is usually ignored in the existing DFM, so that for instance, a single particle rolling on a horizontal plate keeps unreally constant velocity without deceleration. This paper proposes to take account of the rolling friction generated by the elastic hysteresis of particles in the existing DEM. A particle bed in a rotating horizontal cylinder is chosen as a testing model for the numerical simulation to examine the DEM improved in this paper by introducing the rolling friction. The present DEM can explain the rolling, cascading and cataracting flow modes of the particle bed, while the existing DEM cannot do except the rolling mode.