The number (NC) of crazes nucleated by a rubber particle and the breadth (BC) of a craze depend on the particle diameter of rubber by TEM observation of Izod impact fractured specimens. The values of NC and BC were influenced by the deformation degree of the rubber particles. The Izod impact strength was quantitatively explained by total craze volume of whitened region of impact fractured specimens. However this relationship was influenced by the rubber structure (occlusion structure).