PURPOSE: To shorten an operational stopping time by temporarily setting a newly set device at a place where there is no inconvenience in removal of an old device and no inconvenience in moving the new device to a setting place of the old device after removing the old device.

CONSTITUTION: A temporary setting place where there is no inconvenience in removing existing devices 11, 12, 13 and where new devices 1, 2, 3 can be sequentially moved to positions of the existing devices 11-13 is provided, and the newly set devices 1-3 are temporarily set there. Next, cables 11, 21 31 laid in a cable rack are connected to the specified newly set devices 1-3. Thereby, the length of each cable is kept long enough even in the case when each of the newly set devices 1-3 is moved to its specified setting place. Subsequently, operation of the newly set devices 1-3 is started, and the existing devices 11-13 are removed. Thereafter, the newly set device 1 is moved to the position of the existing device 11, the newly set device 2 to the position of the existing device 12 and the newly set device 3 to the position of the existing device 13 respectively.