A film-forming apparatus for forming an impurity-doped film on an object such as a semiconductor wafer has an elongated reaction tube located such that its longitudinal direction is identical to the vertical direction, and having an object arrangement region in which a plurality of objects or semiconductor wafers to be processed can be arranged at intervals in the vertical direction. A film-forming gas is introduced into the reaction tube through a film-forming gas introduction pipe. This apparatus also has a main dopant gas introduction pipe, having a gas outlet located below the object arrangement region in the reaction tube, for introducing a dopant gas into the reaction tube and guiding the same upward, at least one sub dopant gas introduction pipe, having a gas outlet located above the object arrangement region in the reaction tube, for introducing the same dopant gas as the first-mentioned one into the reaction tube so as to compensate for insufficient supply of the dopant gas through the main dopant gas introduction pipe, an exhaustion system for exhausting the gases in the reaction tube, and a heating unit for heating the interior of the reaction tube.