A floating-body type wind power generation device equipped with a floating body, which floats on the surface of water, and a windmill, which is installed on the floating body and at least a portion of which is submersible, said floating-body type wind power generation device being characterized in that the windmill includes at least one blade, a hub attached to the blade, a tower erected on the floating body, a nacelle provide on the tower, a first electrical device provided in the hub or the nacelle, and a second electrical device connected to the first electrical device via a cable, and in that the second electrical device is constructed so as to be capable of relative movement in a direction perpendicular to the tower when the windmill is submerged, so that the second electrical device is not submerged.