Keep the human body cool at an appropriate temperature and ensure sufficient use time. A cold insulator according to one aspect of the present invention is a cold insulator that cools a human body, and includes a frozen material 30a that changes phase at a specific temperature, and a first storage portion that stores the frozen material 30a. The first accommodating portion performs heat transfer between the human body and the frozen material at a contact surface that contacts the skin of the human body, and at least the contact surface can be taken as a heat permeability of the skin of the human body. It has a heat penetration rate that is in the range. The heat permeation rate (J / (m 2 · S1 / 2 · K)) on the contact surface may be 1,000 to 2,000.適切な温度で人体を保冷すると共に、十分な使用時間を確保する。本発明の一態様に係る保冷具は、人体を保冷する保冷具であって、特定の温度で相変化する凍結材３０ａと、前記凍結材３０ａを収容する第１の収容部と、を備え、前記第１の収容部は、人体の皮膚と当接する当接面において、人体と前記凍結材との間の熱伝達を行ない、少なくとも前記当接面は、人体の皮膚の熱浸透率として取り得る範囲内にある熱浸透率を有する。前記当接面における熱浸透率（Ｊ／（ｍ２・Ｓ１／２・Ｋ））は、１，０００～２，０００であっても良い。
