control preparation time in the smbc separation system of fig5 is the same as the control preparation time in the smbc separation system of fig1 because the pump 5 is the same as that in the smbc separation system of fig1 and the set value of the flow rate is the same as that in the smbc separation system of fig1 although one control time is longer thus the time difference between the apparent control preparation time and the actual control preparation time in the smbc separation system of fig5 is a time during which the flow rate control effect is obtained in the smbc separation system of fig5 this time is not included in the apparent flow rate control time therefore even when this time is shortened the separation property enhancement effect by the flow rate control in the smbc separation system of fig5 is not impaired thus in the smbc separation system of fig5 when the switching interval of the flow passages 3 prolonged in accordance with an increase in fill length of the columns is shortened by the above mentioned time difference the supply amounts of the eluant and the material solution and the discharge amounts of the eluants containing an extract and raffinate per unit time can be increased while the flow rate control effect by the pump 5 is obtained compared with the smbc separation system of fig1 therefore the productivity can be further enhanced.