1. A document processing device comprising: a general feature vector memory that stores feature vectors of a shape for each of a plurality of characters; an input unit that optically reads in a document; an extracting unit that extracts feature vectors from the shapes of characters in a document read in by the input unit; a general shape recognition unit that estimates a character for which the feature vectors of its shape extracted by the extracting unit, based on the feature vectors extracted by the extracting unit and the content stored in the general feature vector memory; and a specific feature vector memory that stores the feature vectors extracted by the extracting unit in association with an estimation result of the general shape recognition unit and in association with a character recognition accuracy such that a plurality of feature vectors is associated with a single estimation result.