PURPOSE: To obtain a large-size or extremely large-size container which is excellent in durability, electric insulation, and mechanical strengths by making up the inside layer of a synthetic resin and also making up the outside layer of a resin concrete.

CONSTITUTION: The container 1 is made up of a composite layer consisting of the inside layer 2 and the outside layer 3. The inside layer 2 is made of a chemical- resistant and heat-resistant synthetic resin, e.g., polypropylene, or the like, and its outer surface is provided with the undulation 4. Also, the outside layer 3 is made of a resin concrete containing an aggregate, e.g., the ballast 5, the sand 6, the calcium carbonate 7 or the like, and the thermosetting resin 8 to bind and harden the aggregate, e.g., a polyester resin, an epoxy resin, a phenolic resin, or the like. The container 1 is formed by floating inside layer 2 in a casting mold, for example, and then flowing an unhardened resin concrete into their clearance.