A fuel consumption amount evaluation system is disclosed. The system includes a rotational speed detecting section (5b) for detecting an engine rotational speed of the engine-driven traveling vehicle as a measured rotational speed, an accelerator opening degree detecting section (5a) for detecting an accelerator opening degree, a fuel injection amount calculating means (50) for calculating a fuel injection amount per predetermined unit from the accelerator opening degree and the measured rotational speed, and a mileage evaluating section (54) for effecting a mileage evaluation based on the fuel injection amount calculated by the fuel injection amount calculating means (50).