The effect of molecular weight between cross-links on the abrasion behavior of rubber was investigated using acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), and natural rubber (NR) with a blade abrader. The rate of abrasion was found to be almost constant irrespective of the cross-link density of rubber at low frictional input work, whereas it decreased to a minimum and increased again as frictional input work increased. For rubbers with high cross-link density, it was found that the rate of abrasion increased slowly below the critical frictional input work and increased abruptly above the critical frictional input work. A similar phenomenon was also found in the fatigue test. The values of critical input work in the abrasion test and fatigue test were very close to the fracture energies of rubber. Thus, mechanical fatigue was the major abrasion mechanism below the critical frictional input work and the abrasion mechanism changed from mechanical fatigue to direct tearing at the critical frictional input work. As cross-link density decreased, the critical point in the frictional input work was not observed due to the high fracture energy of rubber. In this range, the abrasion mechanism was the mechanical fatigue, which was confirmed by the fatigue test. However, the critical frictional input work was observed at high test-temperature due to the lowering of the fracture energy. For rubbers with very low cross-link density, a rolling-type abraded surface occurred as a result of the thin surface layer peeling away by abrasion.