Operating device

A torque generating device comprising:

• a magnetic disk configured to have rotational motion around a rotation axis;
• a first yoke located on one side and a second yoke located on an other side across the magnetic disk;
• a coil disposed so as to overlap the magnetic disk when viewed in a direction along a direction in which the rotation axis extends, the coil generating a magnetic field;
• a magnetic viscous fluid filled between the magnetic disk and each of the first yoke and the second yoke;
• a magnetic measurement sensor that measures magnetism caused by a magnetic field using the magnetic viscous fluid, the magnetic disk, the first yoke, and the second yoke as a magnetic path, the magnetic measurement sensor disposed in the magnetic field generated by the coil such that magnetism caused by the magnetic field can be measured, and residual magnetism generated when a current is applied to coil can also be measured;
• and
• a control unit configured to acquire a measured value from the magnetic measurement sensor and control a magnetic field that is generated by the coil based on the measured value to change a viscosity of the magnetic viscous fluid.