A preparation method of silver nanostructure for use as substrate of surface-enhanced Raman scattering (SERS), which can ensure the ‘hot spot’, which provides the considerably very intense electromagnetic field in which the silver nano-structures have uniform average size and very strong forms of particles, by characterizing a variety of conditions such as, for example, concentration of AgNO3 and reductant, reaction temperature, stirring velocity, single dropwise addition quantity, dropwise addition rate, or total dropwise addition quantity, which were unpredictable in the conventional silver nanoparticle preparation method using AgNO3 aqueous solution and NaBH4 reductant, so that the preparation method can be advantageously applied for the mass production of silver nano-structures for use as substrate of SERS because the method can provide multimer form with enhanced SERS signals and reproducibility, and also ability to selectively control the particle size.