Multiple slab waveguides are analyzed by using the transfer matrix method and by introducing a virtual leaky layer. It is shown that the analysis is conceptually equivalent to the prism coupling phenomenon. The Lorentzian function is made use of toobtain the eigenvalues of multiple waveguides. Computer simulations are performed onsingle layered, double layered wavegurdes. The calculation results are confirmed to agree well with those of the finite difference method.