1. An apparatus for detecting a tilt of a document image stored as electronic data, amending the tilt, and recognizing the document image, comprising: character elements extraction means for referring to the document image, and extracting a set of character elements from the document image; line candidate extraction means for referring to the extracted set of character elements, and extracting a candidate for a horizontal character line and a candidate for a vertical character line; line reliability estimation means for estimating reliability of the extracted candidate for the character line; line extraction means for extracting a set of probable lines based on the estimated reliability; and tilt estimation means for estimating a tilt of the document image based on an arrangement of character elements contained in the extracted set of probable lines.