PURPOSE: To perform stirring and mixing in a short time and to prevent yielding of bubbles and the like at the time of stirring, by injecting reagent from a plurality of injecting ports at the bottom part of a reaction tube, with a stirring and reagent injecting nozzle being rotated.

CONSTITUTION: A stirring nozzle 1 is rotated by the rotation of a motor 9, and a conveying-tube fixing table 14 is also rotated. When conveying tubes 2, through which a specified reagent is conveyed, are connected to the stirring nozzle 1 by an O ring, the specified reagent in a reagent bottle 13 is conveyed to the stirring nozzle 1 through a pump 12. Since the conveyed reagent is injected at the bottom of a reaction tube 6 with the stirring nozzle being rotated, stirring efficiency is improved, the reagent can be stirred and mixed with a sample in the reaction tube 6 in a short time, and the yield of bubbles and splashing of the reagent can be suppressed.