In actual rivers, a lot of aquatic plants are often observed and they have significant effects on hydrodynamic properties. The large-scale coherent vortex is generated predominantly in the shear layer near the top of canopy. The downstream advection of these coherent vortices often causes the coherent waving of aquatic vegetation, that is called the “Monami”. The strong oscillations in canopy geometry have the effects of decreasing the amount of vertical turbulent momentum and mass transport into the aquatic canopies. However, there is almost no detailed information about interaction between the flow field and the ‘Monami’ phenomena. Therefore, in the present study, the instantaneous measurements of water velocity and vegetation motion were conducted successfully by the PIV & PTV condition.