To solve the problem of a container house, as features of a container, that the container house is narrow to give feelings of pressure, its look is bad, it is hot in summer and cold in winter since it is easier to use the container house without devising it so much because boring or cutting cannot be performed easily for excellent mobility and high strength.

In a prefabricated container house, a container is disposed on a concrete foundation built higher than GL, a bridge is build across the container for reinforcement, and the bridge and the container are connected by welding. Unnecessary walls and a floor of the container are cut and bored to secure a high roof and a wide indoor space eliminating feelings of pressure. A heat insulating material is taken into the container having the widened indoor space, the ceiling, inner walls and the floor are built up. The outside is covered with waterproof sheets or waterproof materials, heat insulating materials are inserted, the steel-frame base is newly made of steels, the roof is placed over the base, rectangular lumber (steel or wood) is directly mounted by welding or nails, an outer wall member is deposited thereon, and the inside and the outside (the roof and the wall) of the container become a body structure of double structure/double heat insulation.