A heat-sensitive electroresistive composite and a thermostatic heating unit made from the composite. The heat-sensitive electroresistive composites have the property of showing an abrupt variation in electric resistance depending on temperature, and they include organic compounds containing a plural number of alkylene oxides as the unit structure in their molecules and fine pieces of carbon in the form of powder, fiber, whiskers, etc. The above-mentioned organic compounds may be normal chain polyalkylene oxide and its derivatives or cyclic ether compounds. The mixing ratio of organic compounds to the fine pieces of carbon is, for example, 100 to 10-80, but the mixing ratio is not necessarily limited to the range for the other types of organic compounds and fine pieces of carbons. The thermostatic heating units are formed by sealing the heat-sensitive electroresistive composites together with electrodes within insulators. These thermostatic heating units may be a sheet form panel heater using a plastic sheet as the insulator.