The present invention provides a method for efficiently manufacturing a molded foam product having excellent heat insulation, and a molded foam product obtained by such a method. The method of the present invention is a method for manufacturing a molded foam product, including the steps of: melting a resin composition containing a polyolefin and a polylactic acid and impregnating the resin composition with a fluid in a supercritical state to prepare a molten resin, and injecting the molten resin into a cavity formed in a mold and moving a portion of the mold to increase the volume of the cavity before the molten resin injected into the cavity completely solidifies, the fluid impregnated into the resin composition being a fluid of 0.05 to 4.0 wt% inert gas, the molded foam product at least partially having a five-layer cross-sectional structure of a first unfoamed layer, a first foamed layer, a hollow space, a second foamed layer, and a second unfoamed layer included in the given order.