A superconducting magnet for a 40 T hybrid magnet was designed to be as compact as possible, and to be constructed with epoxy-impregnated layer winding using highly strengthened Nb,Sn wires. The magnet generates 16 T in a 420 mm inner diameter of windings. The total coil mass of 4.1 tons, approximately 40 % of the conventional cryostabilized magnet wound with copper-matrix wire was attained.