PURPOSE: To enhance the efficiency of supercritical fluid chromatograph by controlling the pressure being applied to a chromatograph and the line speed of moving phase individually.

CONSTITUTION: A moving phase fluid is fed, by means of a pump 12, from a moving phase source 10 through an injector 14 to a splitter 16 and a sample to be analyzed (not shown) is injected into the flow of moving phase by means of the injector 14. Subsequently, the splitter 16 feeds a part of the mixture of moving phase/sample to a capillary 18 and discharge the residue through an outlet 20. When the moving phase flows through the capillary 18, pressure in the capillary 18 is controlled by means of the pump 12 and the state of pressure in capillary 18 is sustained by fixing a restrictor 22 to the end of outlet of capillary 18. Line speed of moving phase in the restrictor 22 is controlled by regulating the temperature of moving phase fluid through a heater 32 and a temperature controller 34. Since the pressure being applied to chromatograph and the line speed of moving phase are controlled individually by means of the pump 12 and controller 34, efficiency of supercritical fluid chromatograph can be enhanced.