PURPOSE:To cultivate vegetation on and off-shore structure, by a method wherein a vegetation cultivating chamber, a fresh water producer, which makes fresh water from sea water pumped up with the aid of a pump lowered in sea water from a floating wave dissipating levee, and a temperature regulating device for the cultivating chamber through utilization of a solar heat, are mounted on the floating wave dissipating levee. CONSTITUTION:A vegetation cultivating chamber 11 is located on the upper surface of a deck 5 of a floating wave dissipating levee 1, seedbeds 12 and 13 are installed in the cultivating chamber 11, and a temperature regulating device 15 for regulating temperature in the chamber 11 through utilization of a solar heat is provided. Further, a fresh water producer 17 is installed on the floating wave dissipating levee 1, and a submerged pump 18 for pumping up sea water is lowered in sea water from the fresh water producer 17. This permits cultivation of vegetation without using a wide space on a land.