In this paper, human perception ability for robot impedance is analyzed. First, a human-robot system is con-structed using impedance control, where a subject can move the robot freely by his end-point, and two kinds of experiments are performed: single impedance perception and single impedance discrimination. Then, from the experimental results, the accuracy and the differential limen are discussed. Also, it is shown that the human perception ability decreases dramatically under some situations such as multiple impeadace perception and large robot viscosity. The results of the present paper could be effective as basic data in presenting the robot impedance to human operators in the rehabilitation system and human-robot systems.