The present invention aims to provide a method for producing a protein composition, the method being capable of suppressing changes such as degradation and denaturation of a protein which occur when a highly hydrophilic protein or a protein that undergoes denaturation by complete removal of water is irradiated with radiation. The present invention provides a method for producing a protein composition containing a protein (A), a radical scavenger (RS), and at least one hydrogen-bond-formable compound (HC) selected from the group consisting of amino acids, peptides, and proteins other than the protein (A), the method including a sterilization step of radiosterilizing an unsterilized protein composition, wherein the unsterilized protein composition contains the protein (A), the radical scavenger (RS), and the hydrogen-bond-formable compound (HC), the protein (A) contains at least one functional group selected from the group consisting of sulfide, amide, hydroxyl, amino, and carboxyl groups, the hydrogen-bond-formable compound (HC) contains at least one functional group selected from the group consisting of sulfide, amide, hydroxyl, amino, and carboxyl groups, the at least one functional group in the protein (A) is capable of binding to the at least one functional group in the hydrogen-bond-formable compound (HC) via a hydrogen bond, the unsterilized protein composition has a water content of 0 to 30% by weight based on the weight of the unsterilized protein composition, a weight ratio of the radical scavenger (RS) to the protein (A) in the unsterilized protein composition [radical scavenger (RS)/protein (A)] is 0.01 to 1.0, and a molar ratio of a total molar number of functional groups in the hydrogen-bond-formable compound (HC) to a total molar number of functional groups in the protein (A) in the unsterilized protein composition [the total molar number of functional groups in the hydrogen-bond-formable compound (HC)/the total molar number of functional groups in the
