[Object] There are provided an air volume adjustment device and an air-conditioning control system, which can further reduce power consumption in a facility such as a data center. [Solution] An air volume adjustment device 20 is located at a vent for connecting an equipment installation area, where a rack for housing computers is installed, to a free access floor provided below a floor of the equipment installation area and supplied with low-temperature air from an air conditioner. The air volume adjustment device 20 includes an air volume adjustment sheet 22 provided with an opening 27 to allow passage of air, a first roll 21a connected to one end portion of the air volume adjustment sheet 22 and made capable of reeling in the air volume adjustment sheet 22, and a second roll 21b located away from the first roll 21a, connected to another end portion of the air volume adjustment sheet 22, and made capable of reeling in the air volume adjustment sheet 22.