A tissue body formation device 10 for forming a connective tissue body in an environment where a living tissue material is present is provided with: an inner member 20 having a tissue body formation surface that serves as a surface for forming a connective tissue body； and a covering member which is provided with a covering surface that constitutes an external surface of the tissue body formation device, and that covers a part of the tissue body formation surface. The covering member further has a plurality of connection parts that connect the outer side of the tissue body formation device 10 to the tissue body formation surface. Each of the connection parts has an opening in the covering surface. Each of the openings has a minimum dimension of at least 0.5 mm in a direction along the covering surface. The openings account for 20-40% per unit area of the covering surface.
