Provided are the following: a sandwich structure formed from a core component comprising a discontinuous reinforcing fiber, a thermoplastic resin and voids, and a skin component comprising a continuous reinforcing fiber and a matrix resin, wherein in the core component, 30% or more of the discontinuous reinforcing fiber is covered with the thermoplastic resin and monofilaments of the discontinuous reinforcing fiber intersect one another via the thermoplastic resin; an integrally formed article using the sandwich structure; and methods for the production therefor.