To investigate the effect of mechanical parameters on the circulation and its fluctuation in Sagami Bay, baroclinic model experiments were carried out by use of a two-layer source-sink flow in a rotting tank. In the experiment, a simple coastal topography with flat bottom was reproduced. The results show that the path of the Through Flow, which corresponds to the branch current of the Kuroshio, depends on external Rossby number (Ro) and internal Rossby number (Ro^*), and divided into two regimes. For Ro^*≤1.0 in which Rossby internal radius of deformation of the Through Flow is smaller than the width of the approaching channel, the current flows along the Oshima Island as a coastal boundary density current separatd from the western boundary of the channel. For Ro^*>1.0, it changes to a jet flow along the western boundary of the channel, separated from the coast of Oshima Island. The current independent on both Ro and Ro^* in the regime of Ro^*>1.0, Ro≥0.06 and Ro^*≤1.0, Ro≥0.06. The pattern of the cyclonic circulation in the inner part of the bay is also determined by Ro and Ro^*. In case of Ro^*≤, frontal eddies are formed in the northern boundary of the Through Flow. These frontal eddies intrude into the inner part along the eastern boundary of the ay providing vorticity to form and maintain the inner cyclonic circulation. For Ro^*>1.0, the wakes from the Izu peninsula are superposed intensifying the cyclonic circulation. The pattern of the cyclonic circulation is divided into three types; 1) weak cyclonic circulation and the inner anticyclonic circulation (Ro<0.12). 2) cyclonic circulation in the bay (0.12≤Ro<0.25). 3) cyclonic circulation with strong boundary current (Ro≥0.25).