PURPOSE: To obtain a high efficiency and permit the energy economization by constituting an organic composite cycle by gathering a variety of apparatuses utilizing sea-water and exceedingly cutting-off the delivery of the material from the outer field other than the supply of sea-water and discharge of condensed sea-water.

CONSTITUTION: The captioned composite apparatus consists of water production apparatuses 7 and 9 in two stages or more and evaporators 1 and 2 in two stages or more, and further equipped with a generator 4 driven by the turbines 3 and 5 in the heating and regeneration cycle, and further equipped with a mercury-method electrolytic apparatus 11. The sea-water is introduced, and the turbine 3 is driven by the steam generated in the evaporators 1 and 2. The steam after use is introduced into a water production apparatuses 7 and 9, and used as raw material. The condensed sea-water left in the evaporators 1 and 2 is supplied as raw material into the electrolytic apparatus 11.