First of all, in a first step S1, each actuator command value for position command value and posture command value of an end-effector is determined. Next, in a second step S2, rotational resistance values of a first and a second universal joints are obtained, and in a third step S3, the force and the moment exerted to each of the second universal joints are computed using this, and in a fourth step S4, the resultant force and the resultant moment exerted to the end-effector are determined from these. Then, in the fifth step, the elastic deformation amount of a mechanism is computed using these, and a compensation amount of the actuator command value is computed using these values. And then, in the sixth step, the actuator command values determined in the first step are updated with the compensation amount determined in the fifth step taken into account.