Provided is a working medium of the present invention for absorption refrigerators is a mixture that is to contact a carbon steel or a copper alloy that is a structural material of any one of the absorption refrigerators, and includes water and 1,4-dioxane, and further includes a corrosion inhibitor. The corrosion inhibitor includes one or more selected from the group consisting of respective hydroxides of any alkali metal and any alkaline earth metal, and respective oxoates. Thus, corrosion of the structural material of the absorption refrigerator can be restrained.