When injecting a sample into carrier-liquid channels (3A and 3B), injection shock is prevented. Septa 13 and 14 constitute the upper wall and the lower wall of a sample injection part (11) of the carrier-liquid channels (3A and 3B). A needle (27) can vertically penetrate the septum (13) on the upper wall side and also penetrate the septum (14) on the lower wall side. A needle moving unit (28) induces the needle (27) to penetrate the septum (14) on the lower wall side and induces the tip of the needle to face the inside of a sample vessel (26). A measurement pump (29) is operated for drawing and as a result a sample is drawn into the needle (27). Next, the needle (27) is extracted from the septum (14) on the lower wall side, the tip of the needle is induced to face the inside of the sample injection part (11), the measurement pump (29) is caused to discharge and as a result the sample within the needle (27) is injected.
