PROBLEM TO BE SOLVED: To provide an inner stopper as a sealing structure which has sufficient sealing property and safety in a disposable cylindrical container for accommodating blood processing beads and contributes to cost reduction and automation. In a sealing structure of a cylindrical filling port for filling beads provided on a side surface of the cylindrical container, an outer wall surface of the cylindrical filling port includes a fixing claw, and an inner wall surface of the cylindrical filling port. Made of a thermoplastic resin having a tapered portion having a surface facing each other with a gap of 150 μm or less on the narrowed inner wall surface, a bottom portion having a front end surface that is substantially flush with the inner peripheral surface of the container, and a flange portion. The inner plug is welded to the edge of the cylindrical filling port and the collar, and the cover plug is wrapped around the welded inner plug by fitting it with the fixed claw when it is difficult to remove. A usable thermoplastic resin inner stopper having a tapered portion, a bottom portion, and a collar portion； a container for a blood processing module having a sealing structure； a blood processing module in which a blood processing bead is enclosed together with an enclosure liquid. [Selection diagram] Fig. 4【課題】血液処理用ビーズを収容するための使い捨て筒状容器において十分な密閉性、安全性を有し、コストダウン、自動化に寄与する封止構造として中栓の提供。【解決手段】前記筒状容器の側面に設けられたビーズを充填するための筒状充填口の封止構造において、筒状充填口の外壁面が固定爪を備え、筒状充填口の内壁面が窄まっており、窄まった内壁面に１５０μｍ以下の隙間で向かい合う面を有するテーパー部、容器の内周面に略面一で沿う先端面を有する底部、及び鍔部を有する熱可塑性樹脂製中栓が、筒状充填口の縁部と鍔部で溶着されており、かぶせ栓が、取り外し困難な状態で固定爪と嵌合することで溶着された中栓を包み込んでいる封止構造に使用可能な、テーパー部、底部、及び鍔部を有する熱可塑性樹脂製中栓；封止構造を有する血液処理モジュール用容器；容器に封入液とともに血液処理用ビーズが封入された血液処理モジュール。【選択図】図４
