Provided is an interposer for a semiconductor package, the interposer including an interposer substrate comprising a first main surface and a second main surface opposite to the first main surface, a first through-electrode structure and a second through-electrode structure each passing through the interposer substrate and protruding from the first main surface, a connection terminal structure contacting both the first through-electrode structure and the second through-electrode structure, and a photosensitive polymer layer arranged between the connection terminal structure and the interposer substrate, and between the first through-electrode structure and the second through-electrode structure.