The invention provides a pharmaceutical formulation comprising drug-encapsulated polymer micelles formed from a block copolymer having a hydrophilic segment and hydrophobic segment, and has been subjected to high-pressure treatment. The invention also provides a treatment method for a block copolymer having a hydrophilic segment and a hydrophobic segment for formation of drug-encapsulated polymer micelles, the treatment method comprises a step of subjecting the block copolymer to high-pressure treatment.