Abstract: In a ski of the type comprising a hollow core assembly provided with a ski top constituting unit, a ski bottom constituting unit which are firmly laminated to the top side and the bottom side of said hollow core assembly, and side members arranged at the lateral sides of this assembly, the hollow core assembly has, at a substantially central part of the ski relative to the transverse direction of this ski, a hollow structure defined (a) by a longitudinally extending central channel member having a substantially U-shaped cross section and made of a fiber-reinforced plastic, and (b) by a cover plate firmly secured to the end edges of the two legs of said U-shaped central channel member to cover the opening of said U-shape. This core assembly has flanking members made of such material as foamed hard polyurethane resin, wood pieces or honeycomb and securely bonded to the lateral sides of the hollow structure to sandwich the hollow structure therebetween and extending longitudinally of the ski.