An apparatus for producing trichlorosilane, including: a reaction vessel that has a substantially cylindrical wall body, a top plate, and a bottom plate, where a reaction product gas is produced from a raw gas supplied to the reaction vessel through a gas introducing passage provided to the lower section of the cylindrical wall body; and a plurality of heaters that are disposed inside the reaction vessel to heat the raw gas, wherein each of the heaters has a heating element that is elongated in a vertical direction and generates heat by electrification, and a mount that is fixed to the bottom plate and supports the heating element; a flange is provided to intermediate height of the heating element such that the flange is arranged upper than the gas introducing passage and is elongated in horizontal direction; and a passage of the raw gas formed between adjacent heaters is narrowed by the flange.