The invention belongs to the field of cooking devices, and relates to an electric heater, in particular, an electric heater namely a plane heater that can eliminate asymmetric heating even if a secondpattern part is formed on the external side of a first pattern part. The electric heater includes a substrate, a first plane heating element formed on one surface of the substrate, and a second planeheating element formed on one surface of the substrate to be located outside the first plane heating element. The first plane heating element includes a first pattern portion connecting a start pointwith an end point located in a first zone, a pair of first electrodes located outside the first zone, and a pair of first connectors connecting the first pattern portion with the first electrodes. The second plane heating element includes a second pattern portion located in a second zone surrounding the first zone and connecting a start point with an end point, and at least some of the first connectors are located in the second zone.