This flavor source unit (30) is provided with a columnar mass (320) composed of a plurality of flavor pieces and a tubular body (31) for accommodating the columnar mass. The tubular body has: a first tubular body end-face (311) which forms the air inlet end； a second tubular body end-face (313) which forms the air outlet end； and a tubular body side-wall (313) which connects the outer periphery of the first tubular body end-face and the outer periphery of the second tubular body end-face. The columnar mass has: a first mass end-face (321) which forms the air inlet end； a second mass end-face (322) which forms the air outlet end； and a mass side-face (323) which is continuous from the outer periphery of the first mass end-face and the outer periphery of the second mass end-face. The columnar mass is placed such that the space within the tubular body side-wall is infilled by any part of the inner face of the tubular body side-wall coming into contact with the mass side-face. A first space (35) is provided between the first tubular body end-face and first mass end-face and/or between the second tubular body end-face and second mass end-face.
