Nonaqueous electrolyte for sodium secondary cell, and sodium secondary cell

Provided is a nonaqueous electrolyte for a sodium secondary cell, the nonaqueous electrolyte containing a sodium salt, a compound having a sulfur-oxygen bond, and a nonaqueous solvent, the amount of the compound having the sulfur-oxygen bond being within the range of 0.05-10 mass% of the nonaqueous electrolyte. According to the present invention, a nonaqueous electrolyte for a sodium secondary cell having excellent charge-discharge cycle characteristics, and the sodium secondary cell, can be provided, and are industrially useful.