The present disclosure relates to an inorganic binder composition for casting, including: water glass of 40 to 70 parts by weight; nano-silica of 5 to 35 parts by weight; a Li-based water resistant additive of 0.1 to 10 parts by weight; an organic silicon compound of 0.1 to 10 parts by weight; and an anti-sand burning additive of 1 to 10 parts by weight. Furthermore, the present disclosure relates to a core manufactured by using the inorganic binder composition and a cast manufactured so as to include the core.