An electric heater includes a substrate and an inner plane heating element formed on one surface of the substrate. The inner plane heating element includes an inner pattern portion connecting a start point with an end point. The inner pattern portion includes a first track, a second track located outside the first track and spaced part from the first track, a first bridge connecting the first track with one end of the second track, a third track located outside the second track and spaced apart from the second track, and a second bridge connecting the other end of the second track with the third track. A first gap G1 between the first and second tracks is shorter than a second gap G2 between the second and third tracks along a virtual line crossing the first, second and third tracks and closer to the first bridge than the second bridge.