Energy saving control device

A cooperative control unit controls a blind configured by arranging a plurality of slats side by side in an opening of a building, the ascent/descent positions of the slats and the rotation angles of the slats being adjustable. The cooperative control unit is provided with a control unit which performs ascent/descent control for controlling the ascent/descent positions of the slats and opening/closing control for controlling the rotation angles of the slats, and using incident light incident on the interior of the building via the blind, controls the ascent/descent positions of the slats and the rotation angles of the slats in a direction in which the sum of energy consumptions of a lighting load and an air-conditioning load in the building is reduced.