The present invention provides a method for preparing anhydrosugar alcohol, in which the reaction temperature in a vacuum reaction that converts sugar alcohol into anhydrosugar alcohol is controlled to two steps of temperature that is, a first-step low reaction temperature of 100 to 150° C. and a second-step high reaction temperature of 151 to 240° C., so that the selectivity for the intermediate product 1,4-sorbitan can be increased, thereby increasing the yield of anhydrosugar alcohol.