Abstract: A current sensor according to the present invention includes a sensor element and a detector. The sensor element includes a core member, an exciting coil and a detection coil. The sensor element is configured such that, while the exciting coil is fed with an excitation signal, comprising a fundamental component, and when the signal to be detected flows, a signal, including a harmonic component, corresponding to the permeability ? of the core member at that point, being superposed on the fundamental component, is outputted from the detection coil. The detector includes a component extraction unit, a level specification unit, and an information output unit.