Bending test was performed for a micro-sized cantilever specimen that made at Fe-2wt%Sn alloy and the root of the specimen was set to a grain boundary to investigate a condition for grain boundary fracture as a preliminary test for evaluation of grain boundary strength by using an ultramicro hardness tester. The alloy was heated at 600℃ for 5h to cause grain boundary segregation of Sn. The grain boundary was fractured in the bending test for the specimen made at large angle grain boundary; whereas the specimen made at small angle grain boundary was not. This result indicates the possibility that quantitative evaluation for the strength of embrittled grain boundaries can be attained by adopting this experimental method.