To provide a method for promoting protein-mediated reaction by which reduction of reaction efficiency caused by denaturation, deactivation, and the like, of proteins is prevented and desired reaction can be carried out in good reaction efficiency in a short time, and a protein mediated reactor.

The protein mediated reactor has a reaction tank 10 for chemically reacting a substrate in a solvent 5 in the presence of the protein. The reactor is equipped with a pretreatment tank 4 for irradiating electromagnetic waves having about 1cm-100m wave length to the solvent 5 by a microwave irradiator 1 or treating the solvent 5 to boil by a heater 15 or a pressure reduction device, and a means for mixing the protein with the solvent 5. The reaction solution prepared by mixing the protein with the solvent is brought to react in the reaction tank 10. Preferably, a cooling tank 7 is installed to cool the solvent 5 heated in the pretreatment.