In the future, it is expected that robots will play important roles in coexisting with humans. Whenever humans come into contact with these robots they must be able to adjust their physical softness parameters, which will help humans remain calm and which will be favourable for human emotions. Therefore, it is desirable for robots to control their impedance characteristics in such cases. From these points of view, desirable values of the impedance parameters of robots are investigated in this paper through a rating scale method. In terms of the results, the emotions felt by humans with regard to the robots being soft, pleasant and human-like are explained by a linear regression model of the impedance values, and the emotions of being reassuring are classified into four groups.