PURPOSE: To prevent generation of bubbles in a sample solvent channel at the time of sample injection by cleaning a measuring means with a solvent through the solvent inlet port of measuring means when it is coupled with a solvent supply system.

CONSTITUTION: When injection is started, a valve unit C is switched to a position shown by a dashed line where the ports 14, 13, 16 of a valve are coupled, respectively, with ports 15, 18, 17. Under this state, a solvent flows from a solvent supply system through a capillary 1, the ports 16, 17 and a capillary 12 to a chromatograph column. Solvent in measuring section is released into capillaries 10, 19 and collected in a waste liquid container 20. Upon finishing the discharge stage, a needle 8 ascends from a sheet 9 and a sample container 22 is set directly under the needle 8 which then sucks the sample liquid in the container 22. Subsequently, the container 22 is removed, the needle 8 is compressed in the sheet 9, the unit C is switched to a position shown by a solid line and the sample is carried to the column.