A temperature increasing method for a sodium-sulfur battery includes three or more temperature gradients, and inflection points of 90±5° C. and 150±5° C. at which the temperature gradient changes, and the temperature gradient in a section from 90±5° C. to 150±5° C. is 5° C./h or less, whereby it is possible to increase a temperature of the sodium-sulfur battery quickly without affecting the quality of the sodium-sulfur battery.