The effect of the alteration of cold isostatic pressing (CIP) and dewaxing procedures on the pore structure and fracture strength of silicon nitride ceramics was examined. The difference of the fracture strength between two sintered bodies was explained by the pore size variation in ceramics observed in thinned specimens by the transparency technique. It was explained that CIP after dewaxing lowered the compressive strength of the granules in the green body and thus contributed to making the pore size of the sintered body small.