TORQUE SENSOR

A torque sensor of the present invention includes: a ring-shaped deformation body; first to fourth displacement electrodes deformable due to elastic deformation of the ring-shaped deformation body; first to fourth fixed electrodes arranged at positions opposite to those of the first to fourth displacement electrodes; and a detection circuit that outputs an electrical signal representing torque based on a variation amount of capacitance values of first to fourth capacitive elements formed by the first to fourth displacement electrodes and the first to fourth fixed electrodes, wherein the detection circuit outputs, as the electrical signals representing the acting torque, a first electrical signal corresponding to a difference between "a sum of a capacitance value of the first capacitive element and a capacitance value of the second capacitive element" and "a sum of a capacitance value of the third capacitive element and a capacitance value of the fourth capacitive element" and a second electrical signal corresponding to a difference between the capacitance value of the first capacitive element and the capacitance value of the third capacitive element and determines whether the torque sensor is normally functioning based on the first and the second electrical signals.