A magnetic particle type electromagnetic clutch has two clutch discs so disposed that the two discs can be electromagnetically connected together and disconnected. In a space between the two discs are charged magnetic particles. When an excitation current is run through the excitation coil disposed near the two discs to produce a magnetic flux, the two discs and magnetic particles are magnetized to be connected in unison, thereby transmitting a torque from the drive shaft to the driven shaft. The two discs are each secured to the tip end of the shafts. The shaft has two groups of magnetic layers which are rigidly affixed to the shaft and axially spaced. Each of the groups of magnetic layers is directed + 45 degrees or - 45 degrees with respect to the axis of the shaft. When the shafts start to rotate, magnetostriction is developed in the respective magnetic layers resulting in a change in permeability. The change in permeability is causes the change in impedance of a first and second detecting coils so disposed that they face the magnetic layers. The change in impedance is electrical representation of the torque applied to the shafts.
