PURPOSE: To manufacture a laminated hollow molded product which is obtained by laminating a skin layer to one surface of a hollow main body and possessing a high hollow rate even if a molding device to manufacture the skin layer is not provided separately.

CONSTITUTION: Volume of a cavity 3 is reduced to a volume corresponding to a skin layer 6 by approaching a movable side mold 2 to a stationary side mold 1, into which molten resin constituting the skin layer is injected and the skin layer 6 is molded. Then the volume of the cavity 3 is expanded to a volume corresponding to a laminated hollow molded product 9 as the skin layer 6 is dwelled within the cavity 3 by separating the movable side mold 2 from the stationary side mold 1, while injecting or after injection of the molten resin 7a constituting hollow main body into the cavity, a pressurized fluid is pressed into the cavity, a hollow part 8 is expanded and a hollow main body 7 and the skin layer 6 are molded integrally.