According to an embodiment, a smoothing device includes an acquiring unit, a determining unit, and selecting unit. The acquiring unit acquires weather information of a plurality of operation areas. A facility device that performs environmental control according to a control value resulting from operation based on the weather information is installed in each of the operation areas. The determining unit determines whether or not an amount of change in weather exceeds a predetermined first threshold in each of the operation areas. The selecting unit selects at least one first operation area that is an operation area in which the amount of change exceeds the first threshold as a halt area for which the operation of the control value used by the facility device installed in the first operation area is halted when the number of first operation areas exceeds a predetermined second threshold.