A physical quantity detecting apparatus for detecting a physical quantity of an object of measurement. The position of movement of an object of measurement is divided into a given number of segments in advance. The output of a physical quantity sensor for detecting a physical quantity of the object of measurement is calculated on the basis of a correction operation expression which has an independent coefficient group for each segment so as to correct the offset component and the sensitivity. Thus, a physical quantity such as a transmitted torque is detected with high accuracy at real time without being influenced by the fluctuations of the offset output and the sensitivity depending on the position of rotation. The correction operation may also be performed using the temperature dependence function of the offset signal and the temperature dependence function of the sensitivity, thereby enabling the accurate measurement of the physical quantity without the influence of the temperature change.