Method of manufacturing a flexible PTC heating element

The flexible PTC heating element according to the invention has one of the following constitutions. A portion of an electrode (2) and a PTC resistor (3) is impregnated into a flexible substrate (1). A flexible substrate is made of resin foam or rubber material having a concave/convex shape formed on the surface. The flexible PTC heating element has an elongation deformation portion disposed to at least one of an electrode and a PTC resistor. A flexible substrate has adhesiveness and either a flexible substrate or a flexible cover material has an elongation control portion. Therefore, the flexible PTC heating element is highly flexible and excellent in vibration durability.