A composite structure 10 of a resin-diamagnetic material, including a diamagnetic material layer 12 and a resin layer 14 is obtained by a method including disposing particles of a diamagnetic material 22 and a resin 24 in a mold 30, applying a magnetic field to the diamagnetic material 22 disposed in the mold 30, and moving the diamagnetic material 22 in a direction away from at least a part of an inner surface of the mold 30, and then curing the resin 24 in the mold 30 thereby to produce a resin-diamagnetic material composite structure.