A propylene-based copolymer is composed of 60 to 90% by weight of Component (A) that is a polymer component whose major structural unit is a structural unit derived from propylene and 10 to 40% by weight of Component (B) that is a propylene-ethylene copolymer component whose content of a structural unit derived from ethylene is 50 to 80% by weight, wherein the sum total of Component (A) and Component (B) is 100% by weight, wherein the ratio of the intrinsic viscosity of Component (B) ([η]B) to the intrinsic viscosity of Component (A) ([η]A)([η]B/[η]A) satisfies a formula: 1.3