The oxygenator is a housing, a hollow fiber membrane layer in which a plurality of hollow fiber membranes having a gas exchange function are integrated, a lumen of each hollow fiber membrane as a gas channel, and a gas channel. A gas inflow portion and a gas outflow portion provided on the upstream side and the downstream side, respectively, and a blood inflow portion and blood provided on the upstream side and the downstream side of the blood flow channel, respectively, with the outside of each hollow fiber membrane as a blood flow channel A first filter member provided in contact with the outflow portion and the surface of the hollow fiber membrane layer on the blood outflow portion side, covering substantially the entire surface, and having a function of capturing air bubbles in the blood； A second filter member that is spaced from the filter member and disposed between the first filter member and the blood outflow portion and has a function of capturing air bubbles in the blood.人工肺は、ハウジングと、ハウジング内に収納され、ガス交換機能を有する中空糸膜が多数本集積された中空糸膜層と、各中空糸膜の内腔をガス流路として、ガス流路の上流側および下流側にそれぞれ設けられたガス流入部およびガス流出部と、各中空糸膜の外側を血液流路として、血液流路の上流側および下流側にそれぞれ設けられた血液流入部および血液流出部と、中空糸膜層の血液流出部側の面に接して設けられ、面のほぼ全部を覆っており、血液中の気泡を捕捉する機能を有する第１のフィルタ部材と、第１のフィルタ部材から離間して、第１のフィルタ部材と血液流出部との間に配置され、血液中の気泡を捕捉する機能を有する第２のフィルタ部材とを備える。
