The aim of this study is to determine fracture causes of GDC ceramics. GDC ceramics were prepared by sintering Ce_0.9Gd_0.1O₂ powder compacts at 1200, 1300, 1400°C for 2 hours in air. To discuss the effect of doping Gd₂O₃, pure CeO₂ ceramics were also made by sintering at 1300°C. The GDC and CeO₂ ceramics were cut into specimens of 3×4 ×36 mm³ and the fracture strength was measured by four-point bending test. After the test, fracture origins of the GDC and CeO₂ ceramics were identified by SEM fractography. The experimental results suggest that bending strength of GDC was mainly controlled by large pore generated by nonstoichiometry of ceria.