1. A document processing apparatus comprising: block dividing means for dividing input document data into blocks in a predetermined manner according to the structure of the document data; document structuring means for structuring the document data by parsing a block into which the document data is divided by said block dividing means according to the document structure of the block, and by adding tag information to text data constituting the block, said tag information indicating an attribute of the text data; storing means for storing an extraction mode for determining whether or not a sentence is extracted with respect to a tag information added to text data; and sentence extraction means for controlling an extraction of the text data according to the tag information added to the text data by said document structuring means and said extraction mode stored in said storing means.