On the other hand, as the aluminoxane of the component (B-2), there can be mentioned a chain aluminoxane represented by the general formula (XVII) ##STR19## (wherein R22 s are each independently a halogen atom, or a hydrocarbon group such as an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group or an arylalkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and th