The fracture strength of porous ceramics has been studied by many researchers. However, there are few approach on determining fracture mechanism. While fractgraphy is often used to estimate fracture mechanism of dense ceramics. So, in this study, fractography is applied to detect fracture origin of porous ceramics. Porous alumina ceramics (with different porosities 12, 22, 28%) were used. The alumina ceramics were cut into specimens of 5 x 8 x 48 mm, and divided into two groups; polished specimens and as-received specimens. Fracture strengths were measured by 3-point bending test. After the test, fracture origins were identified by optical fractography, and classified into 3 types of defect: inner, surface and edge defects. From the results, we concluded that fractography was the useful technique to understand the fracture mechanism of porous ceramics.