The magnetic sensor is used in various fields such as industrial, automobile, IT and biomagnetism. The MI sensor is a magnetic sensor based on the MI (Magneto Impedance) effect discovered by K. Mori et al. in 1993. The MI element with a pickup coil produced by a plating process is used in electromagnetic compasses. Although it can detect 1–1000 µT level, higher performance in sensitivity and noise level is required. Here, the effect of wire length, magnetic property of the amorphous magnetic wire, the number of coil turns and number of cores on the sensor characteristics was investigated. Then based on the above investigations, the designed MI element was test produced. It was found that the designed element shows dramatically higher sensitivity and 1/100 noise, as compared to the currently used MI element (AMI306).