Provided are a multilayer structure and the like being superior in adhesiveness of an interlayer under high humidity and separability of a barrier layer in water, and even in a case in which the barrier layer is exposed to water in a separating and collecting step, being superior in viscosity stability after separating and collecting a resin that constitutes the barrier layer. The multilayer structure of the present invention is a multilayer structure including a barrier layer (A), a water-soluble layer (B), and an adhesive layer (C), in which: the adhesive layer (C) is laminated via the water-soluble layer (B) on one or both faces of the barrier layer (A); the barrier layer (A) contains a polyamide or an ethylene-vinyl alcohol copolymer (a1) as a principal component; and the water-soluble layer (B) contains an alkali metal ion (b1) at a content of 100 ppm or more and 2,000 ppm or less.