PURPOSE: To judge the quality of instantaneous fuel consumption when a vehicle is running readily, by judging the fuel consumption based of the vehicle based on the number of rotation of an engine and the presence or absence of the pushing of an accel pedal.

CONSTITUTION: The processor of a control circuit 3 reads the number of rotation of an engine E from an engine speed sensor and compares the number of rotation with a limit number of rotation NH, which is stored beforehand. A detected output V of a rack position, which controls the amount of injection of a fuel injection device, from a load sensor 2 is inputted to the processor and compared with a specified value B in the processor. Thus the presence or absence of the pushing of an accel pedal is detected. When E≤NH, it is judged that the fuel consumption is good, and a lamp 4a is lit and displayed. When E>NH and V≥B, the accel pedal is not pushed. Therefore, it is judged that a vehicle is idling or a brake is applied and the fuel consumption is good, and the lamp 4a is lit.