A detector includes a detection winding, a detection winding measurement section, and a detection section. A magnetic core has a hole penetrating the magnetic core along a non-uniform cross section. The detection winding includes a wire inserted into the hole and surrounding a periphery of a detection region that is a part of the non-uniform cross section and has a magnetic flux density different from an average magnetic flux density of the non-uniform cross section. The detection winding measurement section performs a measurement relating to an electromotive force induced by the detection winding. The detection section detects a magnetic bias, a magnetic saturation, or an amount of magnetic flux in the magnetic core based on a measurement result of the detection winding measurement section.