Granules produced to overcome powder handling difficulties must retain their shape during storage or transport but, on the other hand, be easily broken down during designated process. Commonly, granule properties have been evaluated for several properties such as flowability, bulk density, and so forth; however, shape retention and fragility have not yet been evaluated. This study examines whether fragility can be evaluated with attrition tests. We carried out attrition tests with a tapping device on ferric oxide granules and followed the progression of the attrition with time. The attrition mechanism was expressed with an attrition-rate equation with two constants. We showed that these two constants are useful for characterizing the attrition of the granules used in the experiments.