To provide a non-volatile rewritable memory to be used for a vehicle control device, which has a sufficient write-in life without increasing storage capacity.

A range of temperature is set as a predetermined range of temperature tolerance where the number of rewritability of a EEPROM for use in a vehicle control device goes over the minimum required number. Then, when it becomes necessary to write a new data in the EEPROM, the vehicle control device determines whether or not a surrounding temperature of the EEPROM stays continuously as long as one second within the predetermined range of temperature (S14) and runs writing into the EEPROM (S18) only when the surrounding temperature is continuously within the predetermined range of temperature tolerance for one second. A writing is suspended when the surrounding temperature goes out of the predetermined range of temperature tolerance within that one second (S14) or there is some possibility of source voltage not being supplied steadily (S16), but writing is run when the condition like the surrounding temperature etc., is improved thereafter.