A preparative separation/purification system in which a mobile phase containing a target component is passed through a trap column to capture the target component in the trap column and then a first solvent and a second solvent are passed through the trap column, said second solvent having an elution capability and being passed through the trap column to elute the target component from the trap column and collect the target component, the preparative separation/purification system comprising: a) a holding means configured to hold the trap column such that an internal passage of the trap column vertically extends with an inlet end thereof directed downwards and a discharge end thereof directed upwards; b) a liquid supply means configured to supply said second solvent to the inlet end of the trap column, with the target component captured in the trap column held by the holding means, the second solvent having a low solubility to said first solvent remaining in the trap column and having a specific gravity greater than a specific gravity of the first solvent; c) a passage selection means configured to change a passage configuration such that a solution exiting from the discharge end of the trap column is selectively sent to either a collection passage leading to a collection container or a disposal passage leading to a disposal port; d) a computation means for computing a period of time or obtaining a predetermined period of time, said computed period of time or said predetermined period of time being from a point in time when the second solvent begins to be sent to the trap column until the emulsion including the first and second solvents and the target component begins to be discharged from the discharge end of the trap column, the computed period of time being computed from an internal volume of the trap column and a first supply flow rate, which is the flow rate at which the second solvent begins to be sent to the trap column, said predetermined period of time being determined by an experiment or computed in advance; e) a passage control means configured to control the passage selection means such that the first solvent extruded from the discharge end of the trap column is sent to the disposal passage from a point in time when the second solvent begins to be sent by the liquid supply means until said period of time has elapsed, and such that, after said period of time has elapsed, the emulsion is sent to the collection passage; and f) a flow rate control means configured to control the liquid supply means such that the second solvent is supplied at the first supply flow rate from said point in time when the second solvent begins to be sent by the liquid supply means until said period of time has elapsed, and such that, after said period of time has elapsed, the second solvent is supplied at a second supply flow rate which is lower than the first supply flow rate. a) a holding means configured to hold the trap column such that an internal passage of the trap column vertically extends with an inlet end thereof directed downwards and a discharge end thereof directed upwards; b) a liquid supply means configured to supply said second solvent to the inlet end of the trap column, with the target component captured in the trap column held by the holding means, the second solvent having a low solubility to said first solvent remaining in the trap column and having a specific gravity greater than a specific gravity of the first solvent; c) a passage selection means configured to change a passage configuration such that a solution exiting from the discharge end of the trap column is selectively sent to either a collection passage leading to a collection container or a disposal passage leading to a disposal port; d) a computation means for computing a period of time or obtaining a predetermined period of time, said computed period of time or said predetermined period of time being from a point in time when the second solvent begins to be sent to the trap column until the emulsion including the first and second solvents and the target component begins to be discharged from the discharge end of the trap column, the computed period of time being computed from an internal volume of the trap column and a first supply flow rate, which is the flow rate at which the second solvent begins to be sent to the trap column, said predetermined period of time being determined by an experiment or computed in advance; e) a passage control means configured to control the passage selection means such that the first solvent extruded from the discharge end of the trap column is sent to the disposal passage from a point in time when the second solvent begins to be sent by the liquid supply means until said period of time has elapsed, and such that, after said period of time has elapsed, the emulsion is sent to the collection passage; and f) a flow rate control means configured to control the liquid supply means such that the second solvent is supplied at the first supply flow rate from said point in time when the second solvent begins to be sent by the liquid supply means until said period of time has elapsed, and such that, after said period of time has elapsed, the second solvent is supplied at a second supply flow rate which is lower than the first supply flow rate.