PURPOSE: To simplify the constitution for the unit, by halving the mark read-in head, through two divisions of the data column of the mark sheet and reading-in of the split data twice.

CONSTITUTION: After reading in the data at the data column 7 of the mark sheet 4 with the head 2 having a plurality of mark read-in elements 3, this sheet 4 is reversed and the data on the data column 8 is read in at the head 2. In reading in this data, accompanied with the carrying toward A of the sheet 4, the data on the data column 7 is read in the timing of the timing mark 5 toward the arrow B, and the data on the data column 8 of the sheet 4 reversed is read in the timing of the timing mark 6 toward the arrow (c). The reversing of the sheet 4 is made at the sheet carrier of folding system, to reduce the number of the read-in element 3 of the mark read-in head 2 and to simplify the constitution of the unit.