Torque measuring device

A torque measuring device, comprising:

• a coil unit formed into a cylindrical shape as a whole and having a detection coil configured to change a voltage in response to a change in magnetic permeability of a magnetostrictive effect section of a rotating shaft, the magnetic permeability changing according to torque to be transmitted;
• a back yoke formed in a cylindrical shape and arranged coaxially around the coil unit;
• a holder configured to hold the coil unit and the back yoke;
• and
• an electronic circuit including the detection coil and configured to generate an output voltage according to a voltage of the detection coil;
• wherein
• a clearance in a radial direction is provided between an outer peripheral surface of the coil unit and an inner peripheral surface of the back yoke;
• and
• a range of change in the clearance which accompanies temperature change during use is regulated to a range in which a change in the output voltage is linear with respect to the change in the clearance.