An electric heater includes a substrate; and a first plane heating element disposed on one surface of the substrate, in which the first plane heating element includes a first track; a second track spaced apart from the first track; and a third track spaced apart from the second track. At least a portion of the second track is located between the first track and the third track, and the first track and the second track are connected by a first bridge, where the first bridge includes a first outer protrusion protruding toward the third track. The third track is formed with a curved portion which protrudes in an outward direction, and the first outer protrusion faces an inside of the curved portion in the outward direction and is spaced apart from the curved portion.