The processor of a power leveling control device acquires electric cell residue of an electric cell device in each monitoring time, calculates an electric cell residue representative value representing a transition of an electric cell residue in the period based on an acquired electric cell residue, and determines a variation with respect to the current leveling target value based on the electric cell residue representative value. The processor determines a leveling target value changed by the determined variation for power leveling for use in the next period, and controls the power to be supplied from a power supply and an electric cell device to a load based on the leveling target value for power leveling in the next period. Thus, the leveling control may be performed depending on the power supply and the power use situation of a load.