This paper describes a method of generation of a free surface by the boundary integral equation using the poly-harmonic function. This method requires boundary geometry of the free surface and the lines on the free surface, which are, for example, contour lines. The height of points on the free surface is calculated, after solving the discretized boundary integral equation. The complicated free surface must be divided into several free surfaces, the height of which approximately satisfies the Poisson equation. In order to investigate the efficiency of this method, several examples are given.