A method for producing a stabilizer and a heating device allows the entirety of a hollow member to be uniformly heated to a temperature necessary for heat treatment, even in a case in which a cross section varying hollow member is used as the starting material. In a preliminary heating process, energizing heating is performed between electrodes, which are arranged at cross section varying parts at both ends of large cross sectional area part, which can be heated. In an entire heating process, by performing energizing heating between electrodes, which are arranged at both ends of the cross section varying hollow member, the latter can be heated. In the preliminary heating process, it is desirable to perform energization heating at a part having a cross sectional area ratio of 90% or more with respect to the part having a large cross sectional area in the cross section varying part.