The additive for polyolefin resins of this invention is characterized by containing the following fatty alcohol and the following oxyethylene alkyl ether. The fatty alcohol is a one-membered fatty alcohol having 16 to 32 carbon atoms. The oxyethylene alkyl ether is a compound obtained by adding ethylene oxide in an average proportion of less than 2 moles to a one-membered fatty alcohol having 12 to 26 carbon atoms per mole.本發明的聚烯烴系樹脂用添加劑之特徵在於含有下述脂肪醇、以及下述氧乙烯烷基醚。脂肪醇為碳數16~32之一元脂肪醇。氧乙烯烷基醚為對於1莫耳之碳數12~26之一元脂肪醇,將環氧乙烷以平均未達2莫耳的比例加成之化合物。