With the present invention the sheet shaped therapeutic substance can be accurately and easily affixed to the inside of the human body. As shown in FIG. 6A, the sheet shaped substance can be mounted on the head with wrinkles being formed. When this takes place, the sheet shaped substance is held in contact with the outer periphery of the head. Then, by making the pressure of the fluid inside the vent apertures positive, the sheet shaped substance can be blown off. The surface of the head is closely parallel to an inner surface of the esophagus wall for the sheet shaped substance to be affixed. Therefore, this particularly makes it possible to perform such applying step (FIG. 6B) in a more reliable fashion.