Interfacial fracture stresses of carbon/carbon composites were measured by indentation methods. Two types of test methods, namely, single fiber push-out, and bundle fiber push-out tests were conducted. Both methods successfully gave fiber/matrix interface mechanical properties, especially debonding behavior. However, when the interface was strong, the single fiber push-out test encountered technical difficulty in processing the extremely thin specimen required to realize the fiber push out. On the other hand, the bundle fiber push-out test gave a good estimation of interfacial fracture stresses.