To improve operability in transportation, storage and installation, prevent damage and improve recovery and recycling of packaging devices by compression sealing a material of an expanded polyurethane or the like by a double bag, holding it by reinforced corrugated fiberboard plates and binding it with a synthetic resin string.

The material of the expanded polyurethane or the like is received in an inner bag made of a synthetic resin for compression, sealing, and thereafter the sealed material is further received in an outer bag. Then it is held between a pair of reinforced corrugated fiberboard plates and bound with the synthetic resin string.