To immediately answer an accurate delivery of a newly ordered lot and also prevent the delivery of an other specially ordered lot from being delayed when the newly ordered lot is produced.

The line occupying ratios of those lots completed within the previous period are totaled so as to obtain an input capacity in this period (101, 102). Also the line occupying ratios according to the delivery is calculated for each newly ordered lot (104), and their total value is subtracted from the input capacity in this period so as to obtain a residual capacity in this period (105). When the residual capacity in this period is equal or smaller than 0, the delivery of the newly ordered lot or the number of input lots is changed (108), and the calculation is returned to that of the line occupying ratios for the newly ordered lots. When it is larger than O (106), the number of the lots capable of inputting into the residual capacity in this period is determined (109) and the total line occupying ratio of the lots is subtracted from the residual capacity in this period so as to obtain a new residual, capacity in this period (110) which is transferred to the next period as a carry-forward capacity (111).