We study diffusion of a two-dimensional cluster on a two-dimensional surface with immobile impurities. We perform a kinetic Monte Carlo simulation using a simple square lattice model. In our model, not only atoms forming an edge of two-dimensional cluster but also atoms in the cluster, which is neighboring impurities in the cluster, are able to evaporate. The cluster diffusion coefficient in the system with a high impurity concentration is larger than that with no impurities. (C) 2013 Elsevier By. All rights reserved.