The present invention relates to a method for preparing a core-gap-shell nanoparticle having an average height of 0.1 nm to 10 nm, in which a Raman-active material is disposed between a core and a shell, and more specifically, to a method for preparing a core-gap-shell nanoparticle, which comprises introducing a shell made of an alloy of a second metal and a third metal, on the core particles of the first metal, the surface of which is modified with a Raman-active material; selectively removing the second metal by treating with a second metal etchant, followed by dealloying; the core-gap-shell nanoparticle prepared by the above method comprising a Raman-active material disposed in the gap, and uses of the core-gap-shell nanoparticle for biosensing and / or bioimaging.