We have constructed quantum electrodynamics theory for excitons whose center-of-mass motion is confined in arbitrary-structured dielectrics with considering their nonlocal optical susceptibility. We systematically investigate entangled-photon generation via biexcitons in nano-to-macro scale materials by this theory. It is revealed that nano-structured materials provide scattering spectra explicitly reflecting quantum states of confined exciton-polaritons and are promising sources of entangled photons from the viewpoints of both efficiency and signal-to-noise ratio. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim