Abstract: A sheet-like thermal sensing element includes a carbon fiber mixed paper and resin layers laminated on both surfaces of the carbon fiber mixed paper. Electrodes are provided along opposite two sides of the carbon fiber mixed paper. A temperature change can be detected by detecting the change of resistance value of the carbon fiber mixed paper. A sheet-like heater is also disclosed, the heater including a pair of carbon fiber mixed papers separated by an insulating sheet and surrounded by resin. Each of the carbon fiber mixed papers include electrodes thereon. The sheet like heater can both generate heat and detect temperature change for precise heating control. Also disclosed is a method of making both the sheet-like heater and sheet-like thermal sensing element involving producing the carbon fiber mixed paper, electrode formation, laminating the mixed papers together and resin encapsulation.