1. A title extracting apparatus for recognizing and extracting a required partial region from a document image of a document that has been converted into image data, comprising: character region generating means for generating character regions, including black pixel connected regions composed of connected black pixels of the document image; character string region generating means for unifying one or more character regions generated by said character region generating means, and for generating character string regions including one or more character regions; and title extracting means for extracting a particular character string region of the character string regions, according to attributes of a plurality of character string regions generated by said character string region generating means, as a title region, wherein said character region generating means is adapted for obtaining circumscribed rectangles of the black pixel connected regions as the character regions, and wherein said character string region generating means is adapted for generating a histogram of frequency values of lengths of sides of the circumscribed rectangles in the document image, generating a relation table of a predetermined frequency value and a length of a maximum side corresponding to the predetermined frequency value, obtaining a length of a first side, having a high frequency value of the document image, using the relation table, and generating the character string regions corresponding to the length of the first side.