Abstract. When developing the stirring rod for mixing two liquid with which the densities into which gas melted differ in little stirring operation, verification of the stirring effect was performed in the numerical simulation using a vortex method. Since it is calculation for specification examination of the preceding paragraph which creates a producing model, it becomes important to obtain a calculation result early and to feed back to the design. Two dimension calculation of the double file circular cylinder group which carried out staggered arrangement of the nine circular cylinders was performed. The aspects of the flow which strayed off from the design point or the design point were shown. The mixed degree was judged from the degree of the complexity of the flow pattern. In a design point, the complicated flow by a vortex is formed with oscillating 1 period, and interference stirring occurs. Adaptation ranges other than a design point are that the ranges of the value of P/L are 0.8-1.2.