To solve a problem that a conventional mouthpiece with a filter has a complicated constitution, resulting in a high cost, there is provided a mouthpiece, including: a tubular mouthpiece main body that forms a flow path for flowing a breathing gas； a filter placed on the flow path； a tubular insertion member inserted into the mouthpiece main body, wherein the filter has a first filter portion corresponding to a cross-sectional shape of the flow path and a second filter portion folded-back from an outer circumferential edge of the first filter portion, and the second filter portion is sandwiched between an inner circumferential surface of the mouthpiece main body and an outer circumferential surface of the insertion member.本發明之課題，在於習知之附有過濾器之吹嘴，其構造複雜化，且成本變高。本發明之吹嘴具備有：筒狀之吹嘴本體，其形成用以流通呼吸氣之流路；過濾器，其係配置於流路；及筒狀之插入構件，其係插入吹嘴本體之內側。過濾器具有與流路之剖面形狀對應之第1過濾器部分、及自第1過濾器部分之外周緣被回折之第2過濾器部分，且第2過濾器部分被夾持於吹嘴本體之內周面與插入構件之外周面之間。
