In this paper, we propose an efficient up-sampling method of the low-resolution depth map that is obtained by a time-of-flight (TOF) depth sensor. After we capture the color images and TOF depth maps simultaneously using a fusion camera system, each pixel of the low-resolution depth map is relocated to the corresponding color image positions by 3D warping, and the warping error is eliminated in each color segment. Then, we employ a Markov random field (MRF) model to produce a high-resolution disparity map using the warped values and color segment information. Experimental results show that the proposed method efficiently up-sample the low-resolution depth maps compared to the other up-sampling approaches.