PURPOSE: To provide a torque detection method and its apparatus in which the rotating torque of a rotating system can be measured by a simple conversion mechanism.

CONSTITUTION: An apparatus is provided with a component-of-force sensor 6 by which the component of force of the turning force of a rotating body 9 to be measured is detected, with a memory 3 in which a component-of-force/ rotating torque table is stored after the rotating torque of a rotating body as a reference and the output of the component-of-force sensor have been related and with a CPU 2 to which the output of the component-of-force sensor 6 is input so as to be compared with the content of the memory 3 and by which the rotating torque of the rotating body 9 to be measured is detected.