In this paper, we propose a simulation model of uneven terrains based on fractional Brownian motions (fBm) for evaluating traversatility of mobile robots. Using fBm model, one can generate various terrain models by changing only two parameters. We modeled two different terrains by using fBm and checked statistical traversability of a robot with different wheel sizes and body configurations in computer simulation. To validate the effectiveness of the fBm model, we conducted real experiments with a wheeled mobile robot. Probabilities that the robot can travel a certain distance well agreed with the simulation results.