  The coexistent state of the spin density wave (SDW) and the charge density
wave (CDW) in the one-dimensional systems is studied by the mean field
approximation at T=0 in various electron-filling cases. We find that the
coexistent state of SDW and CDW is stabilized when the on-site and the
inter-site Coulomb interactions have the values estimated for the organic
conductors. The ground state energies have cusp-like minima at 1/4, 3/8, 5/12,
7/16, 7/20 and 9/20-fillings.
