A pedal operation amount detecting device in which a brake pedal (11) and a clevis (16) that is fixed to an end of an operation rod (15) are rotatably interconnected by a connection shaft (18), a bush (22) is placed between the brake pedal (11) and the connection shaft (18), and detectors (23, 24) are mounted on the outer peripheral surface of an elastically deformable bush body (22a) of the bush(22). An ECU (25) estimates the angle between the brake pedal (11) and the operation rod (15) based on a ratio between strain loads detected by the detectors (23, 24) and calculates, based on the estimated angle, the amount of operation of the brake pedal (11), or pedal depression force and pedal stroke. The device has simplified structure for improved mountability and highly accurately detects the amount of pedal operation.