A method of producing a silicon carbide sintered body jig using a reaction sintering method, comprising: (a)dispersing a silicon carbide powder and an organic substance as a carbon source in a solvent, to produce a mixed slurry powder, (b) pouring the resulted slurry powder into a mold and drying this to obtain a green body, (c) temporarily-sintering the resulted green body under a vacuum atmosphere at 1800.degree. C., to obtain a temporarily-sintered body, (d) temporarily-molding said temporarily-sintered body, to obtain a temporarily-molded body, (e) impregnating a melted metal silicon into the resulted temporarily-molded body by a capillary phenomenon and reacting free carbon in said temporarily-molded body with silicon sucked into said temporarily-molded body by a capillary phenomenon, to obtain a silicon carbide sintered body, and (f) subjecting the resulted silicon carbide sintered body to precise processing, to obtain a silicon carbide sintered body jig.