Seasonal variation in the estuarine circulation (vertical circulation) in Ise Bay was estimated by a box model analysis using the salinity and river discharge data from 1982 to 1991. The estuarine mixing type of Ise Bay is classified by using the stratification-circulation diagram. Ise Bay is classified into the stratified estuary throughout the year. More than 99% of the total upestuaryward salt flux is caused by the vertical circulation (advection) throughout the year except for January. The vertical diffusion is inert during the strongly stratified period (April - October) and intense during the weakly stratified period (November - March). The maximum and minimum of the vertical circulation occur in February and June, respectively. The corresponding maximum and minimum values of the vertical circulation, upwelling velocity, horizontal velocity in the upper layer and horizontal divergence in the upper layer of the northern division are 8290 m³ s^-1, 1.5 m day^-1, 4.6 cm s^-1 and 2.5×10^-6s^-1 in February and 2300 m³ s^-1, 0.4 m day^-1, 1.6 cm s^-1 and 0.7×10^-6 s^-1 in June, respectively. It is suggested that the intense vertical circulation in winters is driven by the northwesterly monsoon wind.