The present invention relates to a process for preparing cobalt metals by reducing cobalt oxides with ammonia or nitrogen/hydrogen gas mixtures. In accordance with the present invention, a cobalt metal is economically prepared by reacting a cobalt oxide with a nitrogen reductant at a temperature of 300 to 550.degree. C. for 3 to 7 hours, where the nitrogen reductant is injected into a reactor containing the cobalt oxide at a flow rate of 300 to 700 cc/min, preferably 500 cc/min per 1 g of cobalt oxide, while continuously elevating the temperature of the reactor at a rate of 3 to 7.degree. C./min, most preferably 5.degree. C./min.