To provide a method of forming a positive electrode active material with high productivity. To provide a manufacturing apparatus capable of forming a positive electrode active material with high productivity. Provided is a method of forming a positive electrode active material including lithium, a transition metal, oxygen, and fluorine. An adhesion preventing step is performed during heating of an object. Examples of the adhesion preventing step include stirring by rotating a furnace during the heating, stirring by vibrating a container containing an object during the heating, and crushing performed between the plurality of heating steps. By these manufacturing methods, a positive electrode active material having favorable distribution of an additive at the surface portion can be formed.