To provide a floating body structure working system, floating body structure, working ship and floating body structure working method which allow work such as installation and maintenance of a floating structure in a stable state.

A floating body structure working system 1 includes a floating type floating body structure 2 and a working ship 3 for performing at least the installation or maintenance of the floating body structure 2. The floating body structure 2 consists of a pillared column part 4 having a peripheral surface located at the water line when the structure 2 floats, a ballast part 5 arranged below the column part 4 and a flange part 6 arranged at the intermediate part of the column part 4. The working ship 3 includes a gripping part 7 which can be engaged with the flange part 6. The working ship 3 has a lift means for lifting and lowering the floating body structure 2. The floating body structure 2 is fixed to the working ship 3 by lifting and lowering the floating body structure 2 and working ship 3 while the gripping part 7 of the working ship 3 is locked to the flange part 6 of the floating body structure 2 in a floating state.