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., it is one-half or less of the amount of flow of gas stream to be sampled, while the remaining gases in the individual gas streams are collectively exhausted through pressure control means, as desired. In the case of a gas analysis, said sampled single gas stream is supplied to a detector, which, therefore, will produce signals each corresponding to one of said gases. From these signals it is possible to know the concentrations of particular components of the individual gases.