The characteristics of a cluster beam interaction with a solid target are reviewed from the viewpoint of computer simulation. The similarity and dissimilarity of irradiation effects between single and cluster ion beams are mentioned for small clusters. The scaling of the excitation process based on the concept of the stopping force fails for the case of cluster impacts because of the size effect. In the case of a huge cluster with a very low velocity as low as the sound velocity, such a scaling rule is not significant. The Clusterelectric effect is important, thus a new type of algorithm of the “coarse-grained quantum molecular dynamics” that should prove the observed Clusterelectric effect.