To reflect relations of character size or the like suitable for an original sentence in a translated sentence to be added to the original sentence.

A document image processor 10 acquires a document image, sets one or more text regions each including a character string based on the layout of the acquired document image, recognizes the character string included in each set document region, classifies each text region into one or more groups based on the character size and spacing of each text region, translates the recognized character string, determines the character size of the character string translated for each classified group, arranges the character strings of the character size determined for each group into which each text region is classified, and generates an image with the translated sentence added thereto.