A wheeled mobile robot traveling on loose soil has wheels with grousers (i.e., lugs) on their surface to improve its mobility performance. Although previous studies have analysis and modeling of the mobility performance of a wheel with grousers, most of them did not cover the stress distribution of the wheels. In this study, we measured the three-dimensional forces acting on the grouser and three locations of the wheel surface, respectively. The stress distributions generated beneath the wheel with grousers at every angle of the wheel rotation were represented based on the three-dimensional force data. The stress distributions showed that the shear stress hardly affects the wheel surface between each grouser.