The present invention is an invention that aims to provide a technology of designing and evaluating an artificial lung in which performance of each of elements of the artificial lung can be uniformly examined and a generally excellent performance can be exhibited. The present invention provides an artificial lung including a gas exchanger portion that is provided with an external circulation-type gas exchanging hollow fiber membrane bundle and a heat exchanger portion that is provided with a heat exchanging element. A heat exchange performance coefficient of the artificial lung, a blood filling amount of the artificial lung, and a blood side pressure loss of the artificial lung are measured, and when Fp3=heat exchange performance coefficient of artificial lung/(blood filling amount of artificial lungxblood side pressure loss of artificial lung) is calculated, a value of Fp3 is equal to or greater than 0.15.
