The finite element method is widely used as a numerical analysis technique for a field in the engineering field including the electromagnetic field analysis. However, when an analytical field is divided into finite elements, the distribution of finite elements size differs depending on the analyst, and then the accuracy of analysis is influenced by his experience. The study about an adaptive method is making progress in solving this problem. In this study, we suggest an adaptive method by using magnetic flux lines in two-dimensional magnetic field analysis. By using magnetic flux lines, large and small finite elements are generated and distributed at a gentle place and a big place of a change of quantity of physics, respectively. In this paper, we use two models of magnetic field and show the utility of this proposed adaptive method.