In the disclosed vapor deposition method, by using a structure wherein an inner diameter of a group-V source gas introduction piping is greater than an outer diameter a group-III source gas introduction piping, and the group-III source gas introduction piping is inserted one-to-one into the interior of the group-V source gas introduction piping, the group-III source gas piping is thereby prevented from being cooled by a cooling mechanism, and hardening of metallic materials upon the surface of the wall of the piping is alleviated. It is thus possible to provide a vapor deposition device, a vapor deposition method, and a semiconductor element manufacturing method, which are capable of efficaciously introducing easily hardening metallic materials into a reactor without the metallic materials adhering to a showerhead or a piping, and to carry out efficacious doping.