Abstract: In a process for producing a foamed article of a polyolefin resin which comprises filling in a mold pre-foamed particles of a polyolefin resin containing a gaseous mixture consisting of an inorganic gas and a volatile organic blowing agent in their cells and heating them to mold a foamed article; the improvement wherein the pre-foamed particles of the resin are those in which the total pressure of the gaseous mixture is 1.4 to 2.5 kg/cm.sup.2 (abs.), with the partial pressure of the inorganic gas being maintained at 0.4 to 1.1 kg/cm.sup.2 (abs.) and the partial pressure of the volatile blowing agent at 0.8 to 1.6 kg/cm.sup.2 (abs.).