Bending fatigue tests of case-carburized spur gears with different case depths and carburized parts were carried out by two kinds of testing methods. In one method, the load was applied at tooth tip of a test gear by a loading bar. In another method, a meshed gear pair was applied torsional torque. On the basis of these bending fatigue test results and fatigue crack propagations in the face width direction, effects of case depth, carburized part and tooth bearing of case-carburized spur gears were examined. Even in the case where the uniform tooth bearing of meshed gear pair was adjusted by using the red lead, the bending fatigue crack did not uniformly propagated along the face width.