An expandable vinyl chloride resin composition that the expansion ratio of a vinyl chloride resin can be greatly increased by the use of thermally decomposable inorganic blowing agents without the use of organic solvent blowing agents, and which comprises 100 parts by weight of a vinyl chloride resin, 0.5 to 30 parts by weight of, as a processing aid, a (meth)acrylic acid ester polymer having a specific viscosity of not less than 0.73 measured at 30.degree. C. with respect to a solution of 0.1 g of the polymer dissolved in 100 ml of chloroform, and not less than 0.3 to less than 2 parts by weight of a thermally decomposable inorganic blowing agent such as sodium bicarbonate.