To provide a hollow body wherein a hollow element sheet as part of a hollow element and a check valve sheet as part of a check valve are formed by one molded sheet without the need for a check valve manufacturing process as a separate process.

The hollow body 1 comprises the pair of synthetic resin molded sheets 11, 21. The molded sheets 11, 21 consist of hollow element sheets 13, 23 and the check valve sheets 15, 25 connected to connection parts 14, 24 thereof, respectively. The pair of check valve sheets 15, 25 are laid one on the other and thermally welded at their peripheral edges excluding the connection parts 14, 24 with air tightness to form the check valve 3. The pair of hollow element sheets 13, 23 are folded via the connection parts 14, 24, laid one on the other in the state of holding the check valve 3 inside, and thermally welded at their peripheral edges excluding the connection parts 14, 24 with air tightness to form the hollow element 2. The connection parts 14, 24 form an air filling port 38.