A chip PTC thermistor is provided which is capable of increasing the rate of increase in resistance when an overcurrent is applied, thereby increasing the breakdown voltage. The PTC thermistor comprises: a first main electrode and a first sub-electrode disposed on a first face of a conductive polymer with PTC properties; a second main electrode and a second sub-electrode disposed on a second face of the conductive polymer, which is facing the first face; and first and second side electrode and disposed on side faces of the conductive polymer. Cut-off sections are provided to the vicinity of joints of the first main electrode and the first side electrode, and joints of the second main electrode and the second side electrode.