The present invention relates to a solid formulation with improved solubility and maintained stability including a chemical substance poorly soluble in water as a pharmaceutically active ingredient formulated in an improved manner. More specifically, the present invention relates to a solid formulation having improved water-solubility which comprises a chemical substance poorly soluble in water as a pharmaceutically active ingredient, a water-soluble polymer substance and an inorganic porous substance, characterized in that (1) the chemical substance poorly soluble in water forms a solid dispersion together with the water-soluble polymer substance, (2) the water-soluble polymer substance forming the solid dispersion is in the form of fine pieces, and (3) the water-soluble polymer substance is in the form of fine pieces is maintained to be adsorbed on and/or adhered to the surface of the inorganic porous substance. The solid formulation can be produced by stirring and mixing a solution obtained by dissolving a chemical substance poorly soluble in water as a pharmaceutically active ingredient and a water-soluble polymer substance in an organic solvent with an inorganic porous substance and then granulating and drying the mixture.