A medical device configured to enlarge a biological tissue, comprising: an elongated shaft portion; and an expansion body disposed in a distal portion of the shaft portion, and configured to expand and contract in a radial direction, wherein the expansion body has a plurality of wire portions in the circumferential direction linked with the shaft portion, and a torsion restriction portion that connects the wire portions adjacent to each other in the circumferential direction of the expansion body to restrict movement of the plurality of wire portions in a circumferential direction, wherein the expansion body includes a proximal side portion, a central portion and a distal side portion, wherein each of the plurality of the wire portions extends from the proximal portion of the expansion body and is inclined such that a diameter of the expansion body increases toward the central portion of the expansion body, wherein each of the plurality of wire portions includes: a bifurcated portion at an intermediate position toward the central portion of the expansion body in which the wire portion is divided into two thin bifurcated lines; a merging portion in which one of the bifurcated lines merges with a bifurcated line bifurcated from one of the plurality of wire portions adjacent in the circumferential direction such that the bifurcated line serves as the torsion restriction portion; a central wire portion that is located adjacent to the merging portion to form the central portion of the expansion body, and wherein the central wire portion includes recessed portion in the central portion of the expansion body, the recessed portion being recessed in a radial direction, wherein when the distal side portion of the expansion body expands in the radial direction inside a left atrium and the proximal side portion of the expansion body expands in the radial direction inside a right atrium, the recessed portion holds the biological tissue without decreasing a holding force due to the expansion body expanding without any torsion in the circumferential direction by the torsion restriction portion, characterized in that an energy transfer element configured to apply high-frequency energy to an edge portion of a through-hole formed on a biological tissue is disposed on a proximal side surface of the recessed portion. an elongated shaft portion; and an expansion body disposed in a distal portion of the shaft portion, and configured to expand and contract in a radial direction, wherein the expansion body has a plurality of wire portions in the circumferential direction linked with the shaft portion, and a torsion restriction portion that connects the wire portions adjacent to each other in the circumferential direction of the expansion body to restrict movement of the plurality of wire portions in a circumferential direction, wherein the expansion body includes a proximal side portion, a central portion and a distal side portion, wherein each of the plurality of the wire portions extends from the proximal portion of the expansion body and is inclined such that a diameter of the expansion body increases toward the central portion of the expansion body, wherein each of the plurality of wire portions includes: a bifurcated portion at an intermediate position toward the central portion of the expansion body in which the wire portion is divided into two thin bifurcated lines; a merging portion in which one of the bifurcated lines merges with a bifurcated line bifurcated from one of the plurality of wire portions adjacent in the circumferential direction such that the bifurcated line serves as the torsion restriction portion; a central wire portion that is located adjacent to the merging portion to form the central portion of the expansion body, and a bifurcated portion at an intermediate position toward the central portion of the expansion body in which the wire portion is divided into two thin bifurcated lines; a merging portion in which one of the bifurcated lines merges with a bifurcated line bifurcated from one of the plurality of wire portions adjacent in the circumferential direction such that the bifurcated line serves as the torsion restriction portion; a central wire portion that is located adjacent to the merging portion to form the central portion of the expansion body, and wherein the central wire portion includes recessed portion in the central portion of the expansion body, the recessed portion being recessed in a radial direction, wherein when the distal side portion of the expansion body expands in the radial direction inside a left atrium and the proximal side portion of the expansion body expands in the radial direction inside a right atrium, the recessed portion holds the biological tissue without decreasing a holding force due to the expansion body expanding without any torsion in the circumferential direction by the torsion restriction portion, characterized in that an energy transfer element configured to apply high-frequency energy to an edge portion of a through-hole formed on a biological tissue is disposed on a proximal side surface of the recessed portion.