Provided is a resin composition, comprising: an ethylene-vinyl alcohol copolymer (A); an isobutylene-based copolymer (B) containing a halogen atom; and a halogen scavenger (C), wherein a mass ratio (B/A) of the isobutylene-based copolymer (B) to the ethylene-vinyl alcohol copolymer (A) is from 5/95 to 45/55, and a content of the halogen scavenger (C) is from 0.01 to 1 part by mass based on 100 parts by mass of a total of the ethylene-vinyl alcohol copolymer (A) and the isobutylene-based copolymer (B). Such a resin composition is excellent in gas barrier properties and flexibility and stably produced over a long period of time.