Provided are a synthetic resin float unit and a float of which there is no risk of damage by wave movement on the surface of water, and which can be easily assembled even if a floating structure is large in scale; and a floating structure that is not readily susceptible to the effects of wave movement and that has exceptional stability. An articulated synthetic resin float unit for imparting buoyancy to a floating structure placed on the surface of water has an overall cylindrical shape, one end surface thereof being a convex surface, and the other end surface being a concave surface that fits with the convex surface and having a helical projection provided in an outer peripheral surface.