PURPOSE: To obtain the title mixture which can give a foam excellent in heat resistance, by mixing an ethylene polymer with two specified copolymers and a blowing agent.

CONSTITUTION: 0.1W50pts.wt. blowing agent (D) of a decomposition temperature of 50W250°C is added to 100pts.wt. mixture of 40W99.7wt.% PE and/or ethylene/α-olefin copolymer (A) of a density ≥0.900g/cm3 and the number of carbon atoms in the side chain of 1W10 with 1W99wt.% copolymer (B) composed of 30W99.5wt.% ethylene units and 70W0.1wt.% polar monomer units each selected from among an α,β-unsaturated mono- or di-carboxylic acid and its anhydride and half ester, and a copolymer (C) composed of 30W99.5wt.% ethylene units and 70W0.1wt.% ethylenically unsaturated monomer units each containing at least one kind of a polar group selected from hydroxyl and epoxy groups so that the molar ratio of the total of the carboxyl groups and carboxylic anhydride groups of component B to the total of the hydroxyl groups and glycidyl groups of component C may be 0.2W5:1.