In this paper, hydrodynamic effects of 2-dimensional WIG (Wing In Ground effect) moving near the free surface are simulated by means of boundary element techniques. The air flow field around WIG is analyzed by the panel method, and interactions between WIG and the free surface are given as pressure distributions acting on the free surface by this method. In order to analyze the wave making phenomena of water by those pressure distributions, the boundary element method based on Cauchy's integral theorem is employed, in which nonlinearities of free surface conditions can be included. As results of those computations, however, it is verified that wave making effects of WIG are very small because of the difference of fluid density. In final examples of the present computations, simulations of lift changes of WIG moving near the incident regular waves are shown by using the combined scheme of the panel method and the discrete vortex method. In those examples, the wave surface can be treated as the rigid wavy wall, because the wave making effect of WIG is small.