A method for generating a quantum-entangled photon pair is such that a biexciton in such a state that the angular momentum is 0 is generated through two-photon resonance induced by irradiating a semiconductor substance, e.g., CuCl, with two parent photons (angular frequency ωi). A photon pair is then generated by splitting the biexciton thus generated simultaneously into two photons (angular frequencies ωs and ωs′). Since the photon pair is generated by splitting such biexciton having an angular momentum of 0, it has a quantum entanglement with regard to polarization. Since the photon thus generated has a wavelength substantially equal to that of the parent photons, photons of shorter wavelength in a quantum entangled state can be generated.