PROBLEM TO BE SOLVED: To basically cold-insulate the body by evaporation heat of water contained in a wetted base material, and improve shape followability of the base material, and a cooling effect when mounting on a cold storage part of the body.SOLUTION: A dry wet reversible base material 2 comprising a polyvinyl acetal resin porous body is wrapped with a holding material 1 with air permeability, and the holding material 1 is given with a body mounting function for making the base material 2 face a cold storage part of the body. The base material 2 comprises an aggregate of a large number of small pieces 21 of the polyvinyl acetal resin porous body. An apparent average volume of the single small piece 21 is desirably 1 mmto 1,000 mm. The holding material 1 is formed of hydrophilic inner cloth 11 and outer cloth 12.
