This invention provides a structured document processing system comprising: a structured document storage unit for storing a structured document; a partial tree control unit which conceives the structured document stored in the structured document storage unit as a tree structure and controls the tree structure with divided partial trees; an expanding unit which acquires part of the structured document corresponding to a partial tree notified from the partial tree control unit from the structured document storage unit, analyzes part of the acquired structured document from viewpoints of its structure and expands as a hierarchical object in tree structure; and a processing unit for processing the object expanded by the expanding unit following an instruction from a user application.