A chip polymer PTC thermistor for surface mount assembly having a superior long-term connection reliability between side electrode and main and sub electrodes. The thermister comprises; a rectangular parallelepiped conductive polymer(11) having PTC properties; a first main electrode(12a) and a first sub electrode(12b) disposed on a first face of the conductive polymer; a second main electrode(12c) and a second sub electrode(12d) disposed on a second face opposite the first face of the conductive polymer; and first and second side electrodes(13a,13b) folding around and over the entire surface of side faces of the conductive polymer, the side electrodes electrically coupling the electrodes disposed on the two faces of the conductive polymer, and a thickness of the side electrodes is not less than one twentieth of the distance between the first main electrode(12a) and the second sub electrode(12d) and the distance between the first sub electrode(12b) and second main electrode(12a,12c).