Abstract: A continuous sampling flow consisting of a plurality of gases is provided. The sampling of a plurality of gases according to the present invention comprises separately forming continuous gas streams of different gaseous phases, discharging said gas streams simultaneously and continuously into a common definite space in such a manner as to prevent them from mixing together, and sequentially positioning an inlet of open-sampling means successively in said discharged gas streams so that the gases in the individual gas streams are successively sampled and that a single stream formed by the sampled gases from the individual gas streams being in series one after another is taken out. In a preferred embodiment of the invention, the amount of gas sampled from each of said discharged gas streams is such that it will not disturb the discharged gas streams, e.g.