When integrally producing a lamp holder 9, which is provided with a lamp body 3 and a lens portion 4, by using a mold-sliding injection system, a lamp holder 3 having a reflection surface 14 formed on the interior surface thereof is produced. A fixed mold 2 is provided with a vacuum deposition apparatus 5, wherein a lamp holder 9 having a reflection surface is produced by a reflection surface forming process, which is provided between a primary injection process for molding a lamp holder 3 and a lens portion 4 and a secondary injection process for integrating the lamp holder 3 and the lens portion 4 by matching the same together, for vacuum-depositing the reflection surface 14 on the interior surface of the lamp holder 3.