A method for manufacturing a lens module (100) is provided. The lens module includes a flash lamp lens (20) and a holder (10) integrally formed/molded with the lens. The method includes at least three steps. The first step S1 is to mold the lens by means of injecting a first molding material into a provided mold assembly. The second step S2 is to mold the holder integrally with the molded lens by means of injecting a second molding material into the mold assembly to thereby yield the lens module. The third step S3 is to extract the lens module from the mold assembly.