A baking method for heating an object (an inner pipe, an outer pipe) having a vacuum layer formed therein to remove gas molecules occluded in the object, wherein the object itself is made to be a heat production element for heating. By making the baking object a heat production element, the object can be heated directly and the heating can be energy-efficient. Moreover, additional heating means such as a heater or gas is unnecessary, which enables simplification of a configuration of a baking device. Therefore, a baking method is obtained which enables energy-efficient heating and, in particular, uniform heating of a long or large object.