PROBLEM TO BE SOLVED: To provide a floating body structure for wind power generation on the ocean, which suppresses a vibratory force caused by a wind power generator and which can reduce heaving caused by ocean waves.SOLUTION: A floating body structure 10 for being used as a foundation of a wind power generator 12 for wind power generation on the ocean includes a taut mooring rope 14 for tensioning and mooring the floating body structure 10 by connecting the center C of buoyancy of the floating body structure 10 and an anchor 34 together, and an oscillation attenuation mechanism 16 that is interposed between the floating body structure 10 and the taut mooring rope 14 to attenuate heaving of the floating body structure 10.