PURPOSE: To enable automatic control in the pretreatment of various samples, by automatically performing a pretreatment of samples before the samples pass through a detector.

CONSTITUTION: By the operation of a 6-port rotary valve 36, a transfer tube 319 is connected to either a detection passage 39 or a sample pretreating passage 314 and the transfer tube 319 is made smaller in the capacity than a needle 310, a needle seat 311 and an accessary tube to be advantageous for the transferring of a small- capacity sample plug to the passage 39 from the passage 314. Then, the pretreatment of the sample is performed within the passage 314 containing a sample pretreating tube 320 and a syringe 312, a motor 310 is connected to the needle 310 and a container such as sample bottle 316 is made insertable under the needle 310. When the bottle 316 is not under the needle 310, the needle 310 is lowered onto to the needle seat 311 to form a continuous passage from the pretreating tube 320 to a tube 313. An automatic sampler 317 selects the bottle 316 and moreover, the recovery thereof is performed in a controllable manner. Thus, component element such as the syringe 312, the valve 36, the sampler 317 and the motor 315 are controlled with a processor 318 thereby enabling the automation of the sample pretreatment and the sample detection process.