A minimally invasive endoscopic surgical procedure or an endoscopic surgical procedure through natural orifices which includes: introducing a spacial structure in a shrunken state into a body cavity by a spacial structure introduction portion enlarging the spacial structure in the body cavity setting the enlarged spacial structure in a predetermined position in the body cavity and supporting the tissues inside of the body cavity with the set spacial structure inserting a distal end of at least an endoscope or a treatment instrument from at least a part of an opening portion of the spacial structure, and orienting the distal end to a pathological lesion located on the inner side of the tissues inside of the body cavity which is supported by the spacial structure.
