To shorten retrieval time by retrieving a district by utilizing district data obtained by extracting only district data formed by defining an installation place of a device as a dispatching origin from all district data.

Input of a five-digit postal code of the dispatching origin is waited by a CPU 1. And when it is judged that the postal code of the dispatching origin is inputted, whether it is the postal code in the same city or not is judged. When it is judged that the inputted postal code does not exist in a postal code data table in the same city, a prefectural code of a dispatching destination corresponding to upper three digits of the inputted postal code is retrieved from a prefectural code conversion table. Then, the district number corresponding to the retrieved prefectural code is retrieved from a table for retrieving the district number. And the prefectural code with the retrieved district number is decided as the district. Thus, only data on the district number formed by defining the installation place as the dispatching origin are extracted and is stored as the table for retrieving the district number in a ROM 2 simply by inputting the postal code of the number in a ROM 2 simply by inputting the postal code of the installation place of the device.