This study was carried out to establish the optimum condition of cell disruption with a sonicator for the detection of the spore, Bacillus anthracis ${Delta}$-sterne for the purpose of developing automatic fluorometer. The efficiency of sonication on the ${Delta}$-sterne spore disruption was very weak. The ${Delta}$-sterne spore with zirconia bead showed greater disruption than the ${Delta}$-sterne spore alone when sonificated. The volumn of the zirconia bead added in the spore solution has little effect on the disruption efficiency. The detection limit of the ${Delta}$-sterne spore with zirconia bead and the ${Delta}$-sterne spore alone was $10^6$ CFU/mL and $5{ imes}10^7$ CFU/mL respectively, when sample was sonicated for 20 seconds with a sonicator probe of 13 mm diameter.