forcibly open the magnet 82 of the sensor to a predetermined opening degree position when the energizing of the motor 12 is shut out accordingly in the motor vehicle provided with the throttle control apparatus in accordance with the present embodiment the control parameters of the engine are adjusted in correspondence to the change of the electric signal which the hole element 86 outputs in connection with the opening degree of the throttle valve in response to the magnetic signal of the magnet mounted to the axial end of the throttle valve since the sensor is a non contact type the opening signal of the throttle valve 4 corresponding to the change of the electric signal which the hole element 86 outputs is not exposed to a secular change so much so the it is possible to accurately adjust the control parameters of the internal combustion engine for a long period a description will be given of a principle of the sensor with reference to fig7 the magnet 82 corresponding to a rotor of the throttle sensor 80 is fixed to the magnet holder 81 in a state of facing a pair of arc shaped magnets mutually having different polarities to each other when the magnet holder 81 is fixed to the throttle valve 3 and the throttle valve axis 3 is rotated bonding surfaces of.