WORKING SYSTEM FOR FLOATING STRUCTURE, FLOATING STRUCTURE, WORKING SHIP, AND WORKING METHOD FOR FLOATING STRUCTURE

[Summary] [Purpose] To provide a working system for a floating structure, a floating structure, a working ship, and a working method for a floating structure, whereby work such as installation or maintenance of the floating structure can be performed in a stable state. [Means for Attaining the Purpose] A working system 1 of the invention includes a floating type floating structure 2, and a working ship 3 configured to perform at least installation or maintenance of the floating structure 2. The floating structure 2 has a column section 4 whose peripheral surface is located at a waterline when the floating structure is floating, a ballast section 5 arranged below the column section 4, and a flange section 6 arranged at an intermediate portion of the column section 4. The working ship 3 has a gripping section 7 capable of engaging with the flange section 6, and a raising/lowering device 8 configured to raise and lower the floating structure 2. With the gripping section 7 of the working ship 3 engaged with the flange section 6 of the floating structure 2 in a floating state, the floating structure 2 and the working ship 3 are raised or lowered to secure the floating structure 2 to the working ship 3.