Exhaust adapter

The invention provides an exhaust adapter which comprises a non-return structure capable of preventing a non-return function from declining and has the same thickness as an exhaust pipe. The exhaust adapter includes: a cylindrical portion connecting an exhaust pipe of the combustion device to the collection exhaust duct; and a non-return structure for preventing reverse flow of the exhaust gas from the collection exhaust duct side to the exhaust pipe side, the non-return structure including: a shutter support portion including an opening portion through which the exhaust gas from the exhaust pipe passes; an exhaust gas shutter that opens the opening by the pressure of the exhaust gas from the exhaust pipe and closes the opening by self weight when there is no exhaust gas from the exhaust pipe; a support shaft rotatably supporting the exhaust gas damper plate; and a bearing part for supporting the support shaft, so that a pair of shaft hole parts of the exhaust gate plate through which the support shaft is ins