A polypropylene base resin composition for foam-molding which use's a propylenenullnull,null-diene base copolymer containing a small amount of null,null-diene and obtained by copolymerizing propylene with a specific amount of null,null-diene in the presence of a catalyst system for polymerizing olefin comprising a metallocene supported catalyst or a pre-activated metallocene supported catalyst and an organic aluminum compound and which provides a foamed article having uniform and fine foamed cells (bubbles) and a high foaming magnification, a foamable polypropylene base resin composition comprising the propylenenullnull,null-diene base copolymer and a specific amount of a foaming agent, a foamed article obtained by foam-molding the above composition, a production process for the above foamed article and a foam-molded product prepared by heat-molding the above foamed article.