The present invention relates to a solid dispersion characterized in that it comprises carbamic acid 3-(4-benzyloxy-phenyl)-isoxazol-5-ylmethyl ester as an active ingredient and a water-soluble polymer having a glass transition temperature lower than the melting point of the active ingredient as a carrier, and it is prepared via melt extrusion. The solid dispersion of the present invention remarkably increases the solubility and dissolution rate of the active ingredient which is an insoluble drug to efficiently improve the bioavailability when it is orally administered.