According to this invention, a nucleic acid purification instrument whereby it is possible to prevent dispersion of a mist that causes contamination upon discharge of a solution is realized. A pressurizing nozzle 12 is allowed to come into contact with a nucleic acid capturing column 35 so as to closely adhere to the sealing member 36 in a manner such that the sealing member 36 is compressed. Then, an aspiration fan 52 is operated and thus the air in a closed channel (surrounded by a nucleic acid capturing column retention block 37 and a liquid receiving tank 54) flows toward the bottom part of a liquid receiving tank 54 and then flows toward the aspiration fan 52 as a result of installation of a partition board 55. The inside of the nucleic acid capturing column 35 is pressurized using the pressurizing nozzle 12 such that a solution in the nucleic acid capturing column 35 is discharged The discharged solution is gravity-fed to the lower part of a liquid receiving tank 54. When the liquid volume in the nucleic acid capturing column 35 becomes very small, the discharged solution is mixed with air so as to be formed into a mist. The solution exists in a mist form in the middle of an airflow formed by the aspiration fan 52 and the mist flows toward the aspiration fan 52. Then, the mist comprising the solution is captured by a protection filter 51 so as not to be discharged outside the closed channel.