PURPOSE: To be insensitive to a change of a measurement scale interval by providing a magnetic resistance element in a plane parallel to a measurement scale with a gradient to the measuring direction in a scanning unit and magnetically energizing the same with a fixed magnetic field in an auxiliary magnetic field to be inclined to a floating magnetic field for producing the magnetization of the measurement scale.

CONSTITUTION: A length measuring machine 1 comprises a measurement scale 2 having periodic measurement scales and a scanning unit 4 for scanning the scales 3. The measurement scale 2 is magnetized in the opposite directions to each other, and scales 3 are formed. On or more magnetic resistance elements 5 are provided with a gradient of an angle β to the measuring direction (x) in a plane parallel to the scales 3 in a unit 4, and an auxiliary magnetic field Y is applied to the element 5 at an angle of γ to be magnetically energized. The magnetic field Y is vertical to the floating magnetic field X by magnetization of the measurement scale, and the element 5 is shifted at 90 degrees and 0 degrees, respectively to the magnetic fields X, Y. The angles β, γ are preferably 45 degrees, the element 5 forms a half bridge circuit with a fixed resistance. Thus, the work point on a characteristic curve of the element 5 is moved to a linear range, and the frequency of scanning output agrees with the scale period.