An object of the present invention is to prevent stress-corrosion cracking of a header (40) of a reactor. A reactor for producing trichlorosilane by causing metal silicon powder and a hydrogen chloride gas to react with each other includes a cooler (70), the cooler including a plurality of heat transfer medium pipes (30) and a header (40), the plurality of heat transfer medium pipes being provided in a fluid bed (60) inside the reactor, the header being provided in a freeboard section (50) inside the reactor, the header being comprised of a corrosion-resistant material.