PURPOSE: To provide the data setting method which dispenses with a back-up power source and a re-setting operation, and can execute easily re-setting of data by both between devices.

CONSTITUTION: When a return of voltage supply is detected from a stop of voltage supply of a power source control part 43, a slave machine 40 executes a communication processing for requesting a transfer of clock information, executes a transfer request of the clock information to a master machine, and re-sets time if a clock time counting part 41a which is contained, based on the clock information transmitted from the master machine.