Ceramic heater, and glow plug using the same

A ceramic heater, comprising a rodlike heater body (2) configured such that a ceramic resistor (10) formed of an electrically conductive ceramic is embedded in a ceramic substrate (13) formed of an insulating ceramic wherein:

• the ceramic resistor (10) comprises a front end part (11a) disposed at a front end portion of the heater body (2) and is formed of a first electrically conductive ceramic, and two large-diameter rodlike portions (Ld) joined to two end parts of the front end part (11a) as viewed along a direction of electricity supply and forming passages for supplying electricity to the front end part (11a), each of the large-diameter rodlike portions (Ld) extending rearward along a direction of an axis (O) of the heater body (2) and having an electricity-supply sectional area greater than that of the front end part (11a);
• and
• the large-diameter rodlike portions (Ld) each have a connection end part connected to the front end part (11a), the connection end part being formed of the first electrically conductive ceramic and constituting a first resistor portion (11) in cooperation with the front end part (11a), the remaining portion of each of the large-diameter rodlike portions (Ld) is formed of a second electrically conductive ceramic having an electrical resistivity lower than that of the first electrically conductive ceramic and constitutes a second resistor portion (12), and a joint interface (15) between the first resistor portion (11) and the second resistor portion (12) is located within the corresponding large-diameter rodlike portions (Ld).