According to this invention, a document processing method of documenting image data obtained by double-sided scanning of an original containing a single-sided printed part and a double-sided printed part includes a blank determination step of determining on the basis of the image data whether the lower surface of an original is blank, and a documentation step of, when the lower surface is determined in the blank determination step to be blank, saving image data corresponding to the upper surface of the original as document information together with a single-sided printing attribute, and when the lower surface is determined in the blank determination step not to be blank, saving image data corresponding to the two surfaces of the original as document information together with a double-sided printing attribute.