It had been well known that the fracture of SiC manufactured by conventional reaction sintering method was caused by one of the pores in that. However, according to the recent studies, pore free SiC so called APF-SiC was developed by improvement of reaction sintering method. As the result, the strength and the damage tolerance ability rise and then the cause of fracture of APF-SiC changed from pores to something else. Therefore we have investigated fracture surface of APF-SiC by using FE-SEM and EDS in order to demonstrate the cause of fracture. As the result, we found the inclusion that consisted of allotropes of Carbon covered with very thin SiO₂ and SiN layer. And the size of the inclusion is ten times larger than that of SiC grain. Considering from present results, the inclusion is the one of the cause of fracture of APF-SiC.