A power consumption control method comprising: performing a program evaluation and review technique, PERT, analysis, regarding a production line provided with a plurality of processes to be carried out by a plurality of line instruments (3 1 to 3 n), on a process period of the production line based on process information including at least a required period of each of the processes, and a sequence of the processes; performing a process float analysis to obtain a float period for each of the processes based on the PERT analysis; obtaining combinations of the required periods arrangeable within the float periods for the respective processes based on the process float analysis, then obtaining process arrangement combinations being combinations of all the processes used in the combinations of the required periods; selecting one of the process arrangement combinations which has a most leveled sum of power consumption per unit period of the process period; controlling progress of the plurality of processes based on the selected process arrangement combination, and turning off power of the line instrument (3 1 to 3 n) to carry out a process which is not allocated during any period in the process period for the plurality of processes; calculating a total process arrangement combination number m by multiplying all number m' of combinations in each process, the number m' of combinations in each process for which the required period can be split is calculated by m'= ti C xi, while the number m' of combinations in each process for which the required period cannot be split is calculated by m'=(t i -x i)+1, where i is a code of an arbitrary process, x i is the required period for the arbitrary process, and t i is the float period for the arbitrary process; obtaining a sum of power consumption per unit period of the process period for each of the process arrangement combinations in the total process arrangement combination number m based on power consumption per unit period of each of the processes, and obtaining a variance of the sum with respect to set power per unit period being set to the process period, thus obtaining the variances of all of the process arrangement combinations; and selecting, as the selected process arrangement combination, one of the process arrangement combinations which minimizes the variance among all the variances obtained. performing a program evaluation and review technique, PERT, analysis, regarding a production line provided with a plurality of processes to be carried out by a plurality of line instruments (3 1 to 3 n), on a process period of the production line based on process information including at least a required period of each of the processes, and a sequence of the processes; a required period of each of the processes, and a sequence of the processes; performing a process float analysis to obtain a float period for each of the processes based on the PERT analysis; obtaining combinations of the required periods arrangeable within the float periods for the respective processes based on the process float analysis, then obtaining process arrangement combinations being combinations of all the processes used in the combinations of the required periods; selecting one of the process arrangement combinations which has a most leveled sum of power consumption per unit period of the process period; controlling progress of the plurality of processes based on the selected process arrangement combination, and turning off power of the line instrument (3 1 to 3 n) to carry out a process which is not allocated during any period in the process period for the plurality of processes; calculating a total process arrangement combination number m by multiplying all number m' of combinations in each process, the number m' of combinations in each process for which the required period can be split is calculated by m'= ti C xi, while the number m' of combinations in each process for which the required period cannot be split is calculated by m'=(t i -x i)+1, where i is a code of an arbitrary process, x i is the required period for the arbitrary process, and t i is the float period for the arbitrary process; obtaining a sum of power consumption per unit period of the process period for each of the process arrangement combinations in the total process arrangement combination number m based on power consumption per unit period of each of the processes, and obtaining a variance of the sum with respect to set power per unit period being set to the process period, thus obtaining the variances of all of the process arrangement combinations; and selecting, as the selected process arrangement combination, one of the process arrangement combinations which minimizes the variance among all the variances obtained.