To determine an interval (the number of pages or the like) to be changed by counting the number of sheets of paper of a document before changing, and to print only a document to which changing corresponding to the interval is applied, thereby replacing a printed result in the interval.

Print data generation section 20 can designate a first interval (the number of pages or the like) corresponding to a portion to be changed of a document 1 before changing and a second interval corresponding to print data of the portion to be changed. A print section 10 comprises a paper supply section 14 for supplying the document 1 before changing, a count section 15 for counting the number of sheets of paper of the supplied document, and a replacement processing section 16. The replacement processing section 16 judges whether or not an interval of the counted number of sheets is matched with the first interval. When it is matched therewith, the replacement processing section 16 designates the print section 13 to print the print data of the portion to be changed corresponding to the second interval. When it is not, the replacement processing section 16 designates the print section 13 to discharge the document 1 before changing without modification, and then only the first interval of the document 1 before changing is replaced with the document of the changed portion corresponding to the second interval.