We proposed a method of localization for a space rover, which is useful for a rover even on a small planetary body with diameter less than 1000m. It measures round-trip propagation delay between the rover and a mother spacecraft based on radio waves. Together with these measurement data, information of rotational parameters of the small planetary body is used for localization in this method. Simulation results suggested that uncertainty in the direction of the rotation axis of the small planetary body has a serious effect on the localization accuracy. In this paper, a method to estimate the rotational parameters of the small planetary body together with the position of the rover is proposed. Estimation method of the rotational parameters are formulated as an optimization problem. Normal method based on gradient is useless to solve this optimization problem because the performance index has different scales of sensitivity to each estimation parameter. In order to avoid this problem, minimum search based on the gradient was divided into three steps. Numerical simulations assumed a rover on a small planetary body are shown to evaluate the estimation accuracy of the proposed method. Discussions about the sensitivity direction of the proposed method are also described here.