A compatibilizer contains a polymer (A) obtained by reacting a modified olefin-based polymer (a-1) with a polymer (a-2) containing a terminal functional group, wherein the modified olefin-based polymer (a-1) is a polymer modified with from 0.01 to 2 mass % of unsaturated carboxylic acid or a derivative thereof, and the polymer (a-2) is a ring opening polymer or condensation polymer containing a terminal functional group, capable of reacting with the modified olefin-based polymer (a-1), at both ends or one end thereof and has a number average molecular weight from 1,500 to 100,000. This provides an excellent compatibilizer. Particularly, upon melt processing a recovery of a multilayer structure including an EVOH layer and a thermoplastic resin layer, a recycling agent is provided that gives sufficient improvement effects to any of the adhesion of a degraded resin to a screw of a molding machine, the generation of die build-up, the generation of fish eyes, and the decrease in transparency.