The separating and swelling member 110 is named also a balloon for EMR, which is inserted into a body cavity such as the stomach, large intestine, small intestine or esophagus through a clamp channel 12 of FIG. 5 included in an endoscope 10 such as shown in FIG. 16, and then inserted in a submucosal layer 2 below a lesion portion 4 present at a mucosal layer 5 of the body cavity, thereby separatin