To obtain a resin composition having an excellent gas barrier properties by using a plurality of polyalcohols and specifying the relationship between the melting points and densities of the principal member of the polyalcohols and specifying the relationship between the melting points and densities of their subsidiary members.

A polyketone comprising a carbon monoxide/ethylene alternating copolymer is reduced to obtain a polyalcohol (A) comprising above 80% or above repeating units represented by the formula, having an intrinsic viscosity of 0.2-5dl/g (in a water/phenol mixed solvent at 30°C) and having a melting pint TA and a density ρA and a polyalcohol (B) having a melting point TB and a density ρB. Two type of polyalcohols A and B which satisfy the relationship TA-TB≥10 and the relationship ρA-ρB≥0.005 are mixed with each other in a weigh ratio of 97/3 to 55/45, and the obtained mixture is optionally mixed with an antioxidant, an ultraviolet absorber, etc. The resulting mixture is melt- kneaded with a twin-screw extruder and palletized to obtain a resin composition excellent in orientability and thermoformability.