To provide a medical device and a method both of which can suitably embolize a bronchus in a target part by embolizing the bronchus with (at least a part of) a living tissue during surgical treatment of lung emphysema. For example, an injection material is injected into a submucosa by the use of a syringe, and in the injected part, a swelling swollen into the internal cavity of the bronchus is formed to tightly seal the living tissue of the bronchus or a bronchiole, thereby embolizing a target bronchus.