[Object] To provide an oxygenator of a hollow fiber membrane type wherein permeability and exchange ability of oxygen and carbon dioxide gas are excellent, elution into the blood is small, strength is excellent, blood coagulation and plasma leakage are low. [Constitution] An oxygenator of a hollow fiber membrane type where a plurality of hollow fiber membranes are received in a housing, characterized in that at least a part of the regions of contact with the blood of the hollow fiber membrane is coated with a water-insoluble (meth)acrylate copolymer in which a hydrophobic (meth)acrylate is copolymerized with a hydrophilic (meth)acrylate at a molar ratio of (50 to 90) : (50 to 10) (hereinabove, the term "water-insoluble" means that, when 1% by weight of the (meth)acrylate copolymer is allowed to stand for 30 days in 99% by weight (to said copolymer) of a physiological saline solution of 37°C, a weight reduction ratio of said copolymer is not more than 1% by weight).
