1. An inventory managing method for automatically performing an inventory managing process for a management object, comprising the steps of: defining to a node that structures binary tree data to which attributes of the management object are designated to individual hierarchical levels at least the type of an attribute of the management object, the value thereof, an inventory quantity of the management object that satisfies a classification condition represented by the position of the node on the binary tree data, and the relation of a link to another node; designating the attribute and the value of the management object as a retrieving condition when the inventory retrieving process is performed; executing the inventory retrieving process for updating the inventory quantity of each node while searching each node on the binary tree data corresponding to the retrieving condition; and searching each node with priority corresponding to the position of each node in hierarchical layers with attributes that are not included in the retrieving condition.