To enable automatic operation by determining working operating conditions not exceeding upper limit pressure of a pseudo moving bed type separator from the relation between a flow rate of raw material solution and pressure in a single column when the raw material solution is passed through the single column packed with separating packing which is same as those with which columns of the pseudo moving bed type separator is packed.

Through a single column packed with packings which is same as those with which columns of a pseudo moving bed type separator, raw material solution is passed at different flow rates, and pressure of the single column at each flow rate is measured. Each obtained flow rate of the raw material solution and the pressure value in the single column at the flow rate are inputted by an inputting means. From the flow rate value X and the pressure value Y inputted, a linear relational expression, Y=aX+b, is calculated. As an arithmetic means, working operating conditions are determined so that pressure in a zone formed by the column may be within an arbitrary range not exceeding specific system pressure of the pseudo moving bed type separator.