The present invention relates to solubility improving preparation for enhancing the oral absorption of a poorly soluble drug, which is comprising (A) and (B)； (A) a granulated substance which comprises (i) a poorly soluble drug having an acidic group in the molecule, (ii) an alkaline agent, (iii) a surfactant, and this granulated substance dose not substantially contain a disintegrator, (B) a disintegrator existing only in the external of the granulated substance.
