This paper describes distribution, deformation and alteration of the brittle fault rocks from the borehole which penetrated into the Nojima Fault. This fault was activated during the 1995 Hyogoken-Nanbu earthquake (M 7.2) which caused great disasters in the southern part of Kobe City and the northern area of Awaji Island. The active-fault drilling was performed by the Geological Survey of Japan (GSJ) at Nojima Hirabayashi, northwest of Awaji Island and was successful by penetrating the core of the Nojima Fault at 625 m depth.The GSJ core consists of granodiorite including six shear zones, MSZ (main shear zone : 625 m depth), USZ, LSZ-1, LSZ-2, CZ-1 and CZ-2. The former two shear zones are in the hangingwall and the others are in the footwall respectively of the Nojima fault. We have recognized from the core observation that the fault rocks are formed mainly by pulverization and/or alteration. Thus, we proposed a diagram for classification of the fault rocks in the core, on the basis of the degree of pulverization and alteration. Density of cracks and shear surfaces is adopted as pulverization index (plotted on x axis).Relative amounts of residual mafic minerals are selected to represent the degree of alteration (plotted on the y axis). Each axis is divided into four grades and standard samples are selected to represent each intersection point (i.e., 0-0, 0-1, 1-1...3-3.) for classification by unaided eyes.Shear zones are classified into the following three types by using this diagram. Three shear zones, MSZ, USZ and LSZ-1 are characterized by sequential arrangement from the core to margin, of fault gouge, fault breccia, weakly altered and deformed rocks, and host rock. This fault rock distribution is referred to as pulverization - alteration series. The other two shear zones, CZ-1 and CZ-2, are characterized by non-altered- and random-fabric- cataclasites and are referred to as pulverization series. The rest, LSZ-1 is characterized by the complete substitution of the host rock minerals to clay minerals with little pervasive deformation, which is referred to as alteration series. Both pulverization and alteration are characteristic features for formation of fault rocks especially in main shear zone in the hanging wall. In contrast, either pulverization or alteration effect is apparent in separate shear zones in the footwall.