In the design of heat exchanger, it is important to predict the frequency of vortex generated from the finned tube banks in forced convection. This paper described the characteristics of vortex generation in the serrated finned tube banks with staggered arrangement in case of changing the number of finned tube banks and the tube pitch in the flow direction. In consequence we clarified that three kinds of the vortex with the different frequencies (L, M, H type) generated in the low frequency region as well as the spiral finned tube banks, and that UH type vortex having the high frequency generated due to the segmented type fin.