A structural body comprising a substrate and a structural layer formed on the substrate through an air gap in which the structural layer functions as a micro movable element is produced by a process comprising a film-deposition step of successively forming a sacrificial layer made of a silicon oxide film and the structural layer on the substrate, an air gap-forming step of removing the sacrificial layer by etching with a treating fluid to form the air gap between the substrate and the structural layer, and a cleaning step. By using a supercritical carbon dioxide fluid containing a fluorine compound, a water-soluble organic solvent and water as the treating fluid, the sacrificial layer is removed in a short period of time with a small amount of the treating fluid without any damage to the structural body.