When a flow rate of a carrier gas calculated by a column flow rate calculation unit is controlled to be a first flow rate, and when the flow rate of the carrier gas is controlled to be a second flow rate, the flow rates of the carrier gas are detected by a whole flow rate detection unit, and a gas leakage determination unit determines of leakage of the carrier gas on the basis of the rates. Since the flow rate of the carrier gas is changed and the detected value of the whole flow rate detection unit is used at different flow rates, a case can be discriminated where an offset occurs in the detected value of the whole flow rate detection unit and a case where leakage of the carrier gas occurs. Thus, it is satisfactorily determined the presence or absence of the leakage of the carrier gas.