Abstract: A technical object of this invention is to hold down an inflation of an air cushioned portion of an air filled product required to have a high pneumatic pressure of the air chamber with extremely high load F. For the purpose, in a core structure according to this invention in the middle portions of an upper side leather cloth sheet a pair of core members (4) of a double layer structure (1', 2') identical with the leather cloth sheets (1, 2) is provided, and each core member (4) is fused to each of the upper side and lower side leather cloth sheets at both end portion (5), and middle portions (6) of a pair of core members (4) are sewn with a yarn (7) to be coupled. The core structure according to this invention is particularly suitable for holding down the inflation of bouyance adjusting apparatus for scuba diving and the like.