Brittle strength of single crystal silicon is greatly affected by surface etching damage. ICP-etching induced notching is well-known to be most dominant damage in MEMS process. Many experimental approaches toward notching-free process have been carried out. In this study, we have proposed the bending test for evaluating the effect of notching damage on the brittle strength. The test was applied to five kinds of specimens involving identical geometry and different etching damage. Etching damage was quantified by the surface roughness which was measured by laser microscope. It was found that linear relationship between brittle strength and notching roughness can be seen and the strength increases about 200MPa as the roughness decreases 0.1μm.