In treating the fine-particle carrier by the aluminoxane by such a process as above-described (1), (2) and (3) for the preparation of the olefin-polymerizing solid catalyst of the present invention, the aluminoxane supported on the fine-particle carrier may preferably be an aluminoxane precipitated by contacting the aluminoxane solution with a solvent to which the aluminoxane is insoluble or hardl