To provide an angle detection method with which a control for positioning an output shaft using an input shaft encoder and output shaft encoder at a high accuracy and a torsional feedback control can be realized and an angle detection apparatus that executes the angle detection method. In a robot arm constituted by an input shaft encoder, an output shaft encoder, a motor, a reduction gear, and the like, an output shaft encoder detection error is corrected by setting rotation position information using a periodicity of rotations of the input shaft encoder as a reference. When the input/output shaft encoder detection error is corrected in this manner, the control for positioning the output shaft at a high accuracy and the torsional feedback control can be realized.