To obtain digital data indicating the residual of fuel in a fuel tank highly accurately.

A meter ECU converts the output voltage of a potential meter RS and the power source voltage of an on-vehicle battery Ba into digital data. The meter ECU detects an output voltage outputted from resistors RSmax, RSmin for adjustment instead of a sensor output of a vehicle sensor, detects a reference power source voltage outputted from a battery for adjustment, and converts the detected voltages into digital data. The meter ECU calculates digital data indicating an output value in which a detection error due to fluctuation in power source voltage and jumper wires is subtracted from the output voltage of the potential meter RS, on the basis of each of the digital data.