Provided is a method for producing a protein for medical use/polyamino acid complex, the method being able to more stably improve a formation rate (yield) of the protein for medical use/polyamino acid complex.A method for producing a protein for medical use/polyamino acid complex, the method including forming the complex in a mixed solution obtained by mixing a solution A containing a polyamino acid and at least one of alcohol or a hydrophilic polymer with a solution B containing a protein for medical use.