PROBLEM TO BE SOLVED: To provide a medical device and a treatment method, which can be applied to living body lumen in a wider range of inside diameters and can enhance a property of sucking a substance from the inside of a living body lumen by restricting the flow within the living body lumen.SOLUTION: A medical device 10 is inserted into a living body lumen for restricting the flow within the living body lumen, and comprises: an elongated shaft section 23； an expanding section 22 that is an elastically deformable tubular body with a plurality of openings 21A, the expanding section including an outside diameter of central portion greater than that of end portions of both sides of the tubular body in a natural state in which no external forces are applied, with the elongated shaft section 23 being coupled to at least one of the end portions； a flexibly deformable tubular cover section 70 that is coupled to one end portion of the expanding section 22 to surround an outer periphery of the expanding section 22 at the coupled end portion, and that exposed an outer periphery of the expanding section 22 at the other end portion to the outside without surrounding the outer periphery； and a sheath 30 capable of accommodating the expanding section 22 in a diameter-reduced state and the cover section 70.SELECTED DRAWING: Figure 1【課題】適用可能な生体管腔の内径の範囲が広く、生体管腔内の流れを規制して生体管腔内から物質の吸引性を向上させることが可能な医療デバイスおよび処置方法を提供する。【解決手段】生体管腔内に挿入されて当該生体管腔内の流れを規制するための医療デバイス１０であって、長尺なシャフト部２３と、複数の間隙２１Ａを備えて弾性的に変形可能な管体であり、外力の作用しない自然状態において前記管体の両側の端部よりも中央部の外径が大きくなり、端部の少なくとも一方にシャフト部２３が連結された拡張部２２と、拡張部２２の一方の端部に連結されて、当該連結される端部側の拡張部２２の外周を囲むとともに、反対の端部側の拡張部２２の外周を囲まずに外部へ露出させる柔軟に変形可能な筒状のカバー部７０と、縮径させた拡張部２２およびカバー部７０を収容可能なシース３０と、を有する。【選択図】図１
