A method of manufacturing a massive mixture of aluminum nitride and aluminum includes a first heat treatment process of manufacturing the massive mixture of aluminum nitride and aluminum by heating aluminum powder (21) and aluminum pieces (20) inserted into a vessel (13) at a temperature of a melting point of aluminum or higher under a nitrogen atmosphere. An oxide film is formed over the surface of the aluminum powder (21). The oxide film is, for example, a natural oxide film. The weight ratio of the aluminum powder (21) to the aluminum pieces (20) is, for example, 0.1 or less.