1. A network element management method comprising: a mounting schedule input step for receiving as an external input mounting schedule for a physical component detachable from a network element as mounting plan information including a type of the physical component, a scheduled mounting position within the network element, and a scheduled mounting term through a graphical user interface; a determination step for confirming that there is no overlap with a preliminarily provided mounting schedule for another physical component per each predetermined measure of the scheduled mounting position based on the inputted mounting plan information, and for determining that the mounting plan information is implementable only when all of the predetermined measures of the scheduled mounting position are confirmed; a first instance processing step for changing information of a holder class instance already generated in association with all of the predetermined measures of the scheduled mounting position only when the mounting schedule is implementable; and a second instance processing step for generating a physical class instance associated with the holder class instance.