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 gas exchange performance, a heat exchange performance coefficient, a blood filling amount, and a blood side pressure loss are measured, and when Fp=(gas exchange performance×heat exchange performance coefficient)/(blood filling amount×blood side pressure loss) is calculated, a value of Fp ranges from 1.5 to 2.5.
