Abstract: The present invention relates to an air-conditioning and an environmental control device for manufacturing plants of integrated circuits, chemicals and foods, hospitals, etc. where clean air is required. In this environmental control device, controlled air blows out from one side and is absorbed into the other side of the room. The blowing surface and the absorbing surface are divided on the basis of the predetermined module. Ventilating units are formed in a suitable size to conform to the module. Because of the construction, the controlling system of temperature or cleanliness of the air in the environmental control room can be rearranged to an optional one by replacing or changing positions of the ventilating units. Even if a controlling system is rearranged to an optional one, the room should be divided into a supply chamber, a mixing chamber, an environmental control chamber and a return chamber from one side to the opposite side of the room, so that air conditioned can flow as required.