The dominant effect of the interaction between vortices, generated by the addition of the Leading Edge Extension(LEX) in front of the wing, was well observed in this experiment. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vertex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of four angles of attack($15^{circ}$, $20^{circ}$, $25^{circ}$, $30^{circ}$) and six measuring sections(30%, 40%, 50%, 60%, 70%, 80%) of chord length. Distributions of time-averaged velocity vectors and vortices over the delta wing model were compared along the chord length direction. High-speed CCD camera which made it possible to acquire serial images is able to get the detailed information about the flow characteristics occurred on the delta wing. Especially quantitative comparison of the maximum vorticity featuring the induced pressure distribution were also conducted to clarity the significance of the LEX existence.