Abstract: Described is a method for producing a void-containing resin molded product which enables producing a void-containing resin molded product having a high color saturation and an appearance excellent in brightness and heat insulation properties by stretching polymer-molded product containing a single crystalline polymer, and a void-containing resin molded product obtained by the production method. A first aspect of the method for producing a void-containing resin molded product is a method for producing a void-containing resin molded product, the method including: stretching a polymer-molded product containing a single crystalline polymer in at least one axial direction, wherein a yield stress (A) and a stress (L30) at an elongation of 30% in a stress-strain curve of the polymer-molded product in the stretching in the one axial direction satisfy Relationship (I): L30/A<0.