PURPOSE: To easily constitute plates to be composed having a lateral print width larger than the lateral width of a platen, by combining recording papers obtabined by separately recording laterally divided halves, using marks for indicating the central positions of a plate.

CONSTITUTION: The left half of a print in a size of A3 is recorded on a roll of recording paper moving in the arrow direction as a composing plate part 51, and at the same time, the central register marks 6W8 are automtically printed, and successively the right half part 52 of the composing plate as well as the central register marks 11W13 are automatically printed. After the printing, the recording paper is cut at the parts A, B as shown by alternate long and short dash lines, and further at the alternate long and short dash line 9. A composed print of a A3 size is obtained by adhering 2 sheets of the recording paper so as to register both the central marks 6, 11 of the left half and right half and the marks 7, 12, likewise.