Provided is a process for the production of a refractory with high degree of freedom in shape and size, excellent in refractory property and corrosion resistance, and useful as the wall of a refuse incinerator, which process uses, as primary raw material, a melt melted by thermite reaction, and molding it by the use of a room temperature setting binder. The process for producing the refractory of the present invention comprises a melting step of melting ash by thermite reaction, an annealing step of slowly cooling the melt obtained from said melting step, an pulverizing step of pulverizing the cooled slag from said annealing step, an iron removing step of removing the iron from the pulverized slag of said pulverizing step by magnetic dressing, an kneading step of kneading the pulverized slag from said iron removing step with water, a casting step of injecting the kneaded mixture from said kneading step into a mold to harden it, and a drying step of drying the hardened article obtained from said casting step.