In this study, we improve Hisada's (1994) method to efficiently compute Green's functions for viscoelastic layered half-spaces with sources and receivers located at equal or nearly equal depths. Compared with Hisada (1994), we can significantly reduce the range of wavenumber integration especially for the case that sources and receivers are close to the free surface or to boundaries of the source layer. This can be done by deriving analytical asymptotic solutions for both the direct wave and the reflected/transmitted waves from the boundaries, which are neglected in Hisada (1994). We demonstrate the validity and efficiency of our new method for several cases. The FORTRAN codes for this method for both point and dipole sources are open to academic use through anonymous FTP.