Abstract: The mixed powders of a lithium compound and a transition metal based compound are formed into shaped parts, which are packed to form a bed 6 on a porous plate 5 in the bottom of a reaction vessel 7 placed on a support 10 in a firing furnace 8 equipped with an electric heater; the packed parts are fired with an oxidizing gas such as air being forced through the bed 6 at a superficial velocity higher than a specified value via a gas feed pipe 3 connecting an air pump 1, a flow regulator 2 and a preheater 4 and the gas emerging from the bed 6 is discharged into the air atmosphere through a ventilation port 9. Even if increased amounts of the mixed powders have to be fired, the invention process enables the production of a lithium complex oxide as an active material that is homogeneous and which features excellent cell characteristics.