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.