A throttle sensor for an internal combustion engine includes a circuit board and a rotatable body disposed adjacent the circuit board which is connected to the throttle valve and having a pair of brushes disposed in sliding contact with the circuit board. A resistance body, including a basic resistance layer and a protective resistance layer covering a basic resistance layer are formed on the circuit board for engagement by one of the brushes, and a collecting body, including an electric conductive layer and an additional protective resistance layer covering the electric conductive layer is formed on the circuit board for engagement by the other brush. The protective resistance layers protect the basic resistance layers against undue wear and atmospheric conditions.