a plurality of extracting cartridges each having a filter for adsorbing a predetermined substance in a liquid which is injected into the extracting cartridges, respectively;

a rack for holding the extracting cartridges;

a pressurized air introducing mechanism for introducing pressurized air into the extracting cartridges, wherein the pressurized air introducing mechanism is capable of moving vertically with respect to the rack, the pressurized air introducing mechanism including:

a) an air pump for pressurizing air,

b) on-off valves connected to the air pump for turning on and off the introduction of the pressurized air into each of the extracting cartridges, individually, and

c) pressure sensors for detecting an internal pressure within each of the extracting cartridge, respectively, wherein the pressure sensors and the on-off valves correspond to each other in a one-to-one relationship in order to control each of the corresponding extracting cartridges, respectively; and

a control unit for controlling the pressurized air introducing mechanism,

wherein the control unit turns on at least one of the on-off valves in order to introduce the pressurized air into at least one of the extracting cartridges corresponding with the at least one on-off valve in accordance with a result of the detection made by at least one of the pressure sensors corresponding with the at least one on-off valve, and

when the internal pressure detected by at least one of pressure sensors for the at least one extracting cartridge has become equal to a predetermined pressure range for a pressurization upper limit, the control unit turns off the at least one on-off valve in order to confine the area within the at least one extracting cartridge in the pressurized state, the pressure being thereby exerted upon the liquid having been injected into the at least one extracting cartridge.