Disclosed is a pharmaceutical composition which contains medicine containing nanoparticles having an average particle diameter of 10 150 nm said medicine containing nanoparticles being obtained by mixing water with a poorly water soluble medicine containing water miscible solution that contains a poorly water soluble medicine having a water solubility of 50 µg/ml or less a water soluble copolymer having a repeating unit represented by general formula (1) and a water miscible solvent. Also disclosed is a preparation for oral administration which contains the pharmaceutical composition. (In the formula n:m is within the range from 0.25:0.75 to 0.95:0.05 R represents an optionally substituted alkyl group R and R each represents a hydrogen atom or a methyl group and Me represents a methyl group.)0
