The power management system includes: a power management device for managing power to be used by multiple power loads; and a large power-using power load. The large power-using power load is defined as a power load which shows a power consumption larger than a difference between allowable power and an upper limit power smaller than the allowable power when operating at a maximum power consumption. The power management device calculates remaining available power available for the large power-using power load, from the total power consumption of the multiple power loads and the upper limit power, and notifies the remaining available power to the large power-using power load. The large power-using power load starts to operate under a condition that its power consumption is equal to or less than the remaining available power notified by the power management device.