PURPOSE: To improve responsiveness of throttle opening detection at the time of acceleration and deceleration and enable the acceleration and deceleration judgment from a minute accelerator opening by detecting and controlling the treading quantity of the accelerator pedal by the magnitude of dielectric electromotive force and the direction of polarity.

CONSTITUTION: When a signal detected by a detecting means 10 is inputted to an acceleration and deceleration judging means 11, a permanent magnet 5 is moved to right in a detecting coil 6 to make the polarity plus (+) when an accelerator pedal 1 is operated, and accelerating time is judged. When the pedal 1 is released, the permanent magnet 5 is moved to left in the detecting coil 6 to make the polarity minus (-), and decelerating time is judged. Then, when the output signal of the voltage VOUT by dielectric electromotive force measured by the detecting means 10 is inputted to an acceleration and deceleration level judging means 12, a signal SL from a slice level setting means 13 is taken in, and the output voltage VOUT is compared with the slice level voltage SL to determine accelerating level αL, and also, accelerating time αt is calculated in an accelerating and decelerating time calculating part 14.