PROBLEM TO BE SOLVED: To provide a tube connector, an extracorporeal circulation circuit, and a blood purification device which are compact and capable of suppressing retention of air bubbles. SOLUTION: A first connecting part 3 connecting a main tube 11, a second connecting part 4 connecting an ironing tube 13b, a first flow path 3a of the first connecting part 3, and a second connecting part 4 are provided. A communication section 5 having a communication channel 5a that communicates with the second channel 4a, and a main body section 2 in which the first connection section 3, the communication section 5 and the second connection section 4 are sequentially provided in the axial direction. The first flow passage 3a and the second flow passage 4a are formed so as to extend along the axial direction of the main body 2 with a constant diameter, and the diameter of the first flow passage 3a is the second flow passage 4a. The diameter of the communication channel 5a is smaller than that of the first channel 3a, and the communication channel 5a is formed so as to gradually increase in diameter from the first channel 3a side to the second channel 4a side. The central axis C2 of the passage 4a is displaced in the radial direction of the main body 2. [Selection diagram] Figure 2【課題】コンパクトでかつ気泡の滞留を抑制可能なチューブコネクタ、体外循環回路、及び血液浄化装置を提供する。【解決手段】メインチューブ１１を接続する第１接続部３と、被しごきチューブ１３ｂを接続する第２接続部４と、第１接続部３の第１流路３ａと、第２接続部４の第２流路４ａとを連通する連通流路５ａを有する連通部５と、を備え、第１接続部３と連通部５と第２接続部４とを軸方向に順次設けた本体部２を有しており、第１流路３ａ及び第２流路４ａは、一定の径で本体部２の軸方向に沿って延びるように形成され、第１流路３ａの径が第２流路４ａの径よりも小さく、連通流路５ａは、第１流路３ａ側から第２流路４ａ側にかけて徐々に拡径されるよう形成され、第１流路３ａの中心軸Ｃ１と、第２流路４ａの中心軸Ｃ２とが、本体部２の径方向にずれている。【選択図】図２
