Also, the outer layers 132 can be made of a polyvinyl butyral resin (PVB) as a specific material, for example. Polyvinyl butyral resin has excellent adhesiveness to the glass plates and penetration resistance and is thus preferable. On the other hand, the core layer 131 can be made of an ethylene vinyl acetate resin (EVA) or a polyvinyl acetal resin, which is softer than the polyvinyl butyral resin constituting the outer layers. When the soft core layer is interposed between the outer layers, the sound insulation performance can be significantly improved while keeping adhesiveness and penetration resistance that are equivalent to those of a single-layered resin interlayer.