An electric power control apparatus sets a first period for performing electric power control and an overall target amount of power consumption to be consumed by all of a plurality of information processing apparatuses during the first period, calculates an individual target amount of power consumption to be consumed by each information processing apparatus during a plurality of second periods obtained by segmentalizing the first period, based on the first period and the overall target amount, transmits the corresponding second period and the individual target amount to each information processing apparatus, receives an actual usage value of the amount of power consumption in the corresponding second period transmitted from each information processing apparatus, calculates the individual target amount, based on the actual usage value of the amount and the overall target amount, and retransmits the individual target amount to each information processing apparatus.