To provide a sealant film for retort food packaging containers in which heat resistance at retort temperatures is balanced with impact resistance at low temperatures, or a wide processable temperature range is balanced with impact resistance at low temperatures, at a high level beyond the limits of conventional technologies. The object is accomplished by a sealant film for retort food packaging containers having a seal layer, a core layer, and a laminate layer, each comprising a linear polyethylene, wherein each of said layers has a specific density and/or is polymerized by a specific catalyst, or wherein each of said layers has a specific thermal melting rate at 121°C.