In order to investigate the human characteristic on length perception between the thumb and four fingers, we developed a four-degree-of-freedom (4DOF) length display device which can adjust each four distances respectively. The 4DOF device was proofed by length perception experiment. The placement of 4 units of the 4DOF device arranges from fingertip trajectory experimental data. The position of 4 fingers basing on the thumb is changed by stepping motor. The experiment is that each length between the thumb and other four fingers is same length. The results suggested that the same trend of perceptual length by thumb and any other finger is underestimation. In addition, perceptual error around 70mm was the biggest.