[Problems] To provide a torque measurement device capable of more accurately specifying positions of reflectors which are attached to a rotating body, and more accurately obtaining a torque of the rotating body. [Means for Solving Problems] A pair of reflectors (14a, 14b) is provided on the surface of the rotating body (13) and has a spacing in the axial direction, reflected light data obtained by reflection of reflection patterns in the pair of reflectors (14a, 14b) is input and stored, a point of minimizing AIC is determined for a model of the reflected light data from the rotating body (13), and existence regions of the pair of reflectors (14a, 14b) are detected. Then, a twist amount of the rotating body (13) is calculated from the reflector positions specified by the detected existence regions of the pair of reflectors (14a, 14b), and the torque is calculated from the calculated twist amount of the rotating body.