The MI sensor is a magnetic sensor based on the MI (Magneto Impedance) effect discovered by K. Mohri et al. in 1993. A specialized low noise analog output magnetic sensor (nT sensor: MI-CB-1DK) has also been commercialized by AICHI MICRO INTELLIGENT for use in detecting AC magnetic √ fields. According to theoretical analysis, although the √ MI sensor is foreseen to show the fT/ Hz level of noise density, MI-CB-1DK shows 20–30 pT/ Hz at 10 Hz. In this paper, in order to develop an MI element showing lower noise, the effect of the aspect ratio of the amorphous magnetic wire, the number of wires and the effect of electric contact on multiple wires on noise density were investigated. Then an MI element which shows 1/10 the noise density of MI-CB-1DK was developed.