PURPOSE: To obtain an interior material for vehicles, etc. using the heat inertia of thermoforming without requiring an additional preheater, by transferring a core material formed into a prescribed shape by a thermoformer immediately to a vacuum forming mold, and joining a skin material to the core material.

CONSTITUTION: A raw fabric such as resin felts, glass fiber felts, or the like is thermoformed by a thermoforming machine 1 into a prescribed shape, and the resulting core material 2 is tranferred to the vacuum mold 3. At the same time, the ends of the skin material 4 of a synthetic resin or the like are clamped at a clamping position 6, and the skin material 4 is heated by a movable heater 7. After the thermoformed core material 2 having enough heat inertia is placed on the vacuum mold 3, the vacuum mold 3 is moved together with the core material 2 to the clamping position, and a vacuum pump 3a is operated. Consequently, the skin material 4 is drawn onto the thermoformed core material 2, and they are joined by the adhesive constitutent present therebetween to provide the intended interior material 11.