To provide a heat retainer which satisfies the requirements of a user through proper handling without complicated procedures, when a disaster occurs.

This multifunctional heat retainer comprises sheet materialsl formed of flexible cloth, joining means 10A-10C which can join both counter- lateral edge parts 1a, 1b of the sheet materials 1, in a freely detachable manner, so that the sheet materials 1 are formed into a cylindrical shape and a set of opening parts 15, 15 for introducing an arm which can be closed and are provided, at a constant interval, on the sheet 1. In this case, these joining means 10A-10C are provided in at least three blocks or more in the longitudinal direction of both lateral edge parts 1a, 1b of the sheet material so that the almost center parts in the longitudinal direction of the parts 1a, 1b and both end parts in the longitudinal direction of the sheet materials 1 are joined together, respectively.