  We study the electronic states of the anisotropic triangular lattice Hubbard
model at half filling, which is a simple effective model for the organic
superconducting $\kappa$-BEDT-TTF compounds. We treat the effect of the Coulomb
interaction by the fluctuation exchange (FLEX) method, and obtain the phase
diagram of this model for various sets of parameters. It is shown that the
d-wave superconductivity is realized in the wide region of the phase diagram,
next to the antiferromagnetic states. The obtained phase diagram explains the
characters of the experimental results very well.
