The invention provides an oxygenator of a hollow fiber membrane type where a plurality of hollow fiber membranes are received in a housing, wherein at least a part of the regions of the hollow fiber membranes to contact blood during use 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).
