PURPOSE: To provide a magnetostriction type torque sensor which has a large output signal and is stable for a long period by fixing and installing a cylindrical marageing steel to a rotating shaft.

CONSTITUTION: In a magnetostriction type torque sensor formed of a force- fitting member 2 which is fixed and installed to a rotating shaft 1 by force fitting and consists of a cylindrical magnetostrictive alloy whose magnetic permeability is changed according to an added torque; an exciting means 3 for adding a magnetic field to the force-fitting member 2; a signal detecting means for sensing the change of the magnetic permeability of the magnetostrictive alloy resulted from the torque in non-contact; and a torque converting circuit for converting the electric signal from the signal detecting means 3 into the magnitude of the torque, a marageing steel is used in the force-fitting member 2.