An elastomer composition comprising a butyl-based rubber (A), as a dispersed phase, including (i) a brominated isobutylene and p-methylstyrene copolymer rubber or (ii) a blend of a butyl rubber, halogenated butyl rubber and/or polyisobutylene rubber and a brominated isobutylene and p-methylstyrene copolymer rubber and a Nylon resin (B), as a matrix phase, selected from Nylon 11, Nylon 6/66 copolymer, Nylon 6 and/or Nylon 66, wherein the matrix phase of the butyl-based rubber/Nylon resin blend composition having titanium oxide (C) compounded therein in an amount of 2.5 to 8% by weight, based upon the weight of the Nylon resin (B), whereby UV degradation can be suppressed and long term outdoor exposure can be withstood and a pneumatic tire using the same.