Recently, a sensor structure consisting of magnetic wires attached directly to a rotating shaft, a pick-up coil, and a pair of magnets separately located outside the rotor was proposed. This paper presents a structure whose excitation source is just a single magnet. This structure decreases the cost of the previous sensor while retaining its advantages. For example, multiple output signals can be obtained per turn of the shaft by simply adding a corresponding number of wires, without requiring more pick-up coils and magnet pairs. In this study, the dependence of the output voltage on the pick-up coil was measured and the domain wall structure was elucidated by the measurement result.