A method of recycling a battery pack (10) that includes an assembled battery composed of a plurality of electric cells that are connected in series to one another includes a heating process of heating the battery pack (10) by supplying a vapor supplied from a vapor boiler (14) into a heat treatment bath (12) for heating the battery pack (10) to replace a space in the heat treatment bath (12) with the vapor, and a condensation process of condensing thermolysis products, which are discharged from the battery pack (10) through the heating process, by a condenser (18).