the present invention provides a method for producing an expanded fiber - reinforced thermoplastic resin molding , the method using a mold comprising a female and male dies and comprising processes for supplying a molten thermoplastic resin containing reinforcing fibers whose average fiber length is maintained at 1 mm or more to between the female and male dies to charge a mold cavity with the molten thermoplastic resin , opening a part or the whole of the mold in the thickness direction of a molding after the charging , and cooling a molding while maintaining a cavity clearance at the thickness of a final molding , the method wherein the mold cavity of the mold is interconnectable to the atmosphere , the method further comprising steps for forming a solidified layer in the surface of the molten thermoplastic resin charged in the mold cavity , followed by breaking at least a part of the solidified surface layer , introducing the air through the broken part concurrently with or after the breakage , and opening a part or the whole of the mold concurrently with the introduction of the air so that a cavity clearance defined there reaches the thickness of the final molding , thereby making the internal unsolidified molten , thermoplastic resin expand , said method being able to easily produce expanded fiber - reinforced thermoplastic resin moldings with high expansion ratios and excellent in light - weight property , high - strength and surface transferability .