[PROBLEMS] To increase the rate of gas transfer in gas exchangers.[MEANS FOR SOLVING PROBLEMS] A gas exchange chip comprises substrates (1,2); two flow channels (3,4) formed in the substrates (1,2) and each having an inlet port and an outlet port; and multiple grooves (9) interlinking the flow channels (3,4). The grooves (9) have the size of their sectional area predetermined and have at least a part of the internal surface thereof rendered hydrophobic so as to permit the transfer of gas component while inhibiting any liquid passage. A sample water containing carbon dioxide is caused to flow through one of the flow channels (3) while pure water is caused to flow through the other flow channel (4) to thereby transfer the carbon dioxide contained in the sample water into the pure water.