Tensioning and tension-measuring device of at least one rope for electric energy wind generators, comprising: - at least one first supporting means arranged to support a first end of said rope; - at least one second supporting means arranged to support a second end of said rope, said second end being connectable to a working load; - at least one mobile tensioning means equipped with at least one third supporting means arranged to support an intermediate section of said rope interposed between said first and said second supporting means, said intermediate section being arranged to be included between said first end and said second end of said rope, said third supporting means of said mobile tensioning means being arranged to be taken in compression of said intermediate section of said rope through the action of at least one elastic means; - at least one measuring means, adapted to measure at least one value χ of a linear distance d or an angular distance α included between a reference point and a position of said measuring means and to send said value χ to at least one processing means adapted to indirectly compute a value σ of tension of said rope through a function σ = f(χ, k), where k is an elastic coefficient of said elastic means, characterized in that said mobile tensioning means is composed of at least one tensioning lever oscillating around its own rotation axis and said measuring means is at least one inclination meter adapted to measure at least one of said values χ of an angle of said angular distance α included between said reference point and an angular position of said tensioning lever and to send said value χ to said processing means adapted to indirectly compute said value σ of tension of said rope through said function σ = f(χ, k), where k is said elastic coefficient of said elastic means and χ = α, and in that it comprises at least one braking means adapted to block by contact and/or friction at least said intermediate section of said rope under the compression action of said third supporting means against said braking means under the action of said elastic means. - at least one first supporting means arranged to support a first end of said rope; - at least one second supporting means arranged to support a second end of said rope, said second end being connectable to a working load; - at least one mobile tensioning means equipped with at least one third supporting means arranged to support an intermediate section of said rope interposed between said first and said second supporting means, said intermediate section being arranged to be included between said first end and said second end of said rope, said third supporting means of said mobile tensioning means being arranged to be taken in compression of said intermediate section of said rope through the action of at least one elastic means; - at least one measuring means, adapted to measure at least one value χ of a linear distance d or an angular distance α included between a reference point and a position of said measuring means and to send said value χ to at least one processing means adapted to indirectly compute a value σ of tension of said rope through a function σ = f(χ, k), where k is an elastic coefficient of said elastic means,