PURPOSE: To minimize changes in sensitivity over a wide temperature range, by a method wherein a plurality of magnetic resistors are formed on the same pellet and with the minimization of a temperature characteristic difference therebetween, a magnetic bias is applied with a magnet to the respective resistors to set amplification factors of first and second amplification circuits divided to a specified value.

CONSTITUTION: First to sixth electric resistors RM1WRM6 and P1WP10 as input/ output terminals thereof are formed on an alumina substrate 11 of a magnetic body detector. A pattern should be such that the center-to-center distance L of the resistors RM1 and RM2 is a half a pitch of magnetic teeth while other resistors RM3WRM6 are folded once. The positions of the resistors RM1WRM3 are separated to the right and left from the positions of those RM5, RM4 and RM6 and a magnetoresistance element pellet 10 thus arranged is baked on an alumina substrate 12 to be mounted on a hybrid IC substrate 15. A bias magnetic field is applied to the resistors RM1WRM3 and RM5 with a magnet and an amplification factor of a first amplifier of an amplification circuit 16 is determined by the resistors RM3 and RM5 while an amplification factor of a second amplifier done by the resistors RM4 and RM6.