Low noise MI sensor (MI-CB-1DK, shows 20 pT/Hz0.5 at 10 Hz of noise density [1] based on amorphous magnetic wire has been commercialized in 2006, and has been used for detecting foreign ferrous particles in various products such as foods, medicines and industrial products produced in factories. In the case of foreign particles detection, it is required to detect foreign ferrous particles with a size of less than 1mm (especially around 0.3 mm), therefore the demand for magnetic sensor increases for tinier field detection. From such a background, we previously reported the development of low noise MI sensor by the design of amorphous magnetic wire and MI element[1]. And the research of biomagnetic measurement using this MI element has also been reported[2].