A vehicle device is provided that includes a first processer for processing first data classified as a first category when being supplied based on a vehicle-mounted power source, a second processor for processing second data classified as a second category when being supplied based on the vehicle-mounted power source, an external data storage externally attached to both the first and second processors, and a built-in data storage provided in the second processor and capable of retaining the stored second data even if a battery voltage decreases to a predetermined value for a predetermined period of time. At least one of the first and second processors varies a storage destination and a storage frequency in accordance with priorities. The second processor constantly stores at least part of the second data in the built-in data storage.