In a pedal operation amount detecting apparatus, a brake pedal and a crevice fixed to an end portion of an operation rod are rotatably coupled by a coupling shaft, a bush is interposed between the brake pedal and the coupling shaft, and detectors are mounted on an outer peripheral surface of a bush body, which is elastically deformable, in the bush, and an ECU estimates an angle between the brake pedal and the operation rod based on a ratio between distortion loads detected by the detectors, and calculates an operation amount of the brake pedal, that is to say, pedal force and a pedal stroke, based on the angle, thereby enabling to improve mountability by simplifying a configuration and to detect the operation amount with a high degree of accuracy.