The beta-crystal nucleating effect on polypropylene has been compared between gamma-quinacridone and quinacridonequinone. While the beta-crystal does not form at gamma-quinacridone content below 1 ppm where red coloring is recognized on the molded article, much beta-crystal forms even at quinacridonequinone content below 1 ppm where brown coloring is not recognized on the molded article. This means that the beta-crystal nucleating ability of quinacridonequinone is superior to that of gamma-quinacridone. However, both nucleators show a similar change in the physical properties of injection molded article against nucleator content.