PURPOSE: To correctingly process the data to a process data value (k) so that the integral number value of mile data of a count control part at supplying power is not less than the integral number value of the mile data at cutting power by outputting a correction control signal (q) to the count control part at resupplying power.
CONSTITUTION: A pulse signal (p) is outputted to a count control part 3 from a running distance sensor 1 of a wheel 8 at every a decided running distance, in the control part 3, the integral number value of kilometer data counted from the signal (p) is memorized in EEPROM 4 in order, and the decimal number value to one place of decimals is memorized in C-MOS 7 in order, and the kilometer data is output to a display device 2 to display in kilometer. At cutting off power, the decimal number value of the kilometer data is eliminated but the integral number value is stored in the EEPROM 4. At re-supplying power, a power supply detecting sensor 6 is actuated to output a detected signal (r) to a correction process control part 5 to actuate the control part 5, and a signal (q) is output to the control part 3. By this signal (q), the kilometer data stored in the EEPROM 4 at supplying power is correctingly processed to a process data value (k), and from the process data value (k) by counting of the pulse signal (q) estimation of the data is reopened.