The present disclosure relates to a sodium-ion storage material and an electrode material for a sodium-ion battery, an electrode material for a seawater battery, an electrode for a sodium-ion battery, an electrode for a seawater battery, a sodium-ion battery, and a seawater battery, which include the sodium-ion storage material. Specifically, the sodium-ion storage material may include one or more materials selected from the group consisting of CuxS, FeS, FeS2, Ni3S, NbS2, SbOx, SbSx, SnS and SnS2, wherein 0<x≤2. When the sodium-ion storage material according to the present disclosure is used, it may exhibit high discharge capacity, and when the sodium-ion storage material is applied to a sodium-ion battery which is a secondary battery, it may exhibit excellent charge/discharge cycle characteristics.