[Problem] There has been a requirement for a process for producing a pharmaceutical preparation that is obtained by encapsulating a uniform poorly water-soluble drug in a block copolymer, and dissolves immediately with an addition of water, and does not contain residues of organic solvents. [Solution] Provided is a method for producing a drug-block copolymer composite, the method comprising: mixing a poorly water-soluble drug and a block copolymer including a hydrophilic segment and a hydrophobic segment bonded together, in one or more non-aqueous solvents； optionally heating the mixture as necessary； and spray-drying the resulting mixture liquid.
