A supply-demand control device connected through a communication network to a charge-discharge control device to control charge and discharge of a power storage device connected to a power distribution line in a power distribution system managed by a community, the supply-demand control device including a load and power-generation-amount estimation unit to estimate a load and a power generation amount as a planned load and power generation amount; a first-evaluation-function calculation unit to calculate a value of a first evaluation function, which is a sum of a power purchase cost, a natural-discharge loss cost, a storage-battery life-span cost, a power-transmission loss cost, and a charge-discharge loss cost; a planned charge-discharge command calculation unit to calculate the charge-discharge command amount by which the first evaluation function is minimized; and a power-purchase plan output unit to create a power purchase plan based on the charge-discharge command.