This paper proposes a parameter designing method for a hexapod robot by utilizing formal verification. The robot is controlled based on follow-the-contact-point gait control and is possible to walk over uneven terrain. The allowable contacting area of each leg is a crucial parameter for walk performance and is the target to be designed in this paper. Behavior of each leg of the robot is modelled by a timed-automaton, and specifications that the robot should satisfy to keep satable walk are expressed by computational tree logic. And then, upper and lower bounds of time parameters in the timed-automaton is derived based on the proposed argorithm utilizing model checking. The robot can take and change behavior arbitrarily in the derived time parameter space. Finally, the allowable contact area of each leg is derived from the upper and lower bounds of time parameters. Validity of the proposed method is verified by simulation using physics engine of a hexapod robot.