In this paper, we investigate a simple movable projection mapping system which can reduce distortion and fluctuation of a projected image by assisting a gimbal device by geometric image transformation. Since a conventional gimbal device can compensate the movement of a mounted projector only, we design a new gimbal device which can compensate the relative geometrical relationship between the projector and the screen as well. The proposed method stabilizes a projected image using the newly designed gimbal which tracks the screen with a visual marker placed at each vertex and transforms the shape of image. Through an experiment, we evaluate the performance of the proposed projected image stabilization technique.