PURPOSE: To obtain an automatic splitter for a gas chromatograph with which environments can be rapidly set and which can perform highly reproducible analysis.

CONSTITUTION: A carrier gas flow path 11 is equipped with a flow rate sensor 2 and a pressure sensor 4, a first variable valve 3 is provided between a carrier gas inlet part 1 and a splitting part 5, and a second variable valve 7 is provided on a split line 12. The first and second variable valves 3,7 are controlled by outputs of the flow rate sensor 2 and the pressure sensor 4, while the outputs of the flow rate sensor 2 and the pressure sensor 4 are equipped respectively with at least two control paths, wherein one of them is selected and transmitted to the first and second variable valves 3,7.