A final purpose of this study is to design a dexterity assistance system for operating a machine. In order to design a dexterity assistance system, analysis of human characteristics is necessary. And the study of stabilizing operation of an inverted pendulum is important for understanding the neural control of balance and skill acquisition. Therefore, this study focuses on stabilizing operation of an inverted pendulum, and analyzes the dexterity process of human operation. This paper assumes that the human operation is PD control. And feedback gains are identified at each danger in the operation, and relationship between the results of identification and skill level is discussed. Furthermore, we verify the proposed operation analysis technique by the variation of the order of the human controller.