An electric heater, comprising: an outer frame; and a heating core disposed within the outer frame and defining first and second ends, at least one of the first and second ends being configured to connect to a power source; wherein the heating core comprises: a plurality of heat dissipating components, wherein the heat dissipating component preferably comprises two connecting sheets and a heat dissipating sheet disposed between the two connecting sheets, and the heat dissipating sheet preferably comprises a corrugated aluminum sheet, a plurality of heating components, the heating components and the heat dissipating components being arranged alternately, and adjacent heating component and heat dissipating component being spaced apart from each other and connected with each other via a thermally conductive silicone rubber, the heating component comprising a core tube and a positive temperature coefficient thermistor disposed in the core tube wherein the heating component preferably further comprises an insulating member disposed between the core tube and the positive temperature coefficient thermistor, and the insulating member comprises a ceramic plate, preferably further comprising a protective tube disposed on at least one side of the heating core, and a sealing-waterproof glue layer coated on the sealing-waterproof glue member, characterized in that the electric heater further comprises: a sealing-waterproof glue member disposed within the outer frame and configured to encase the at least one of the first and second, preferably both ends of the heating core. an outer frame; and a heating core disposed within the outer frame and defining first and second ends, at least one of the first and second ends being configured to connect to a power source; wherein the heating core comprises: a plurality of heat dissipating components, wherein the heat dissipating component preferably comprises two connecting sheets and a heat dissipating sheet disposed between the two connecting sheets, and the heat dissipating sheet preferably comprises a corrugated aluminum sheet, a plurality of heating components, the heating components and the heat dissipating components being arranged alternately, and adjacent heating component and heat dissipating component being spaced apart from each other and connected with each other via a thermally conductive silicone rubber, the heating component comprising a core tube and a positive temperature coefficient thermistor disposed in the core tube wherein the heating component preferably further comprises an insulating member disposed between the core tube and the positive temperature coefficient thermistor, and the insulating member comprises a ceramic plate, a plurality of heat dissipating components, wherein the heat dissipating component preferably comprises two connecting sheets and a heat dissipating sheet disposed between the two connecting sheets, and the heat dissipating sheet preferably comprises a corrugated aluminum sheet, a plurality of heating components, the heating components and the heat dissipating components being arranged alternately, and adjacent heating component and heat dissipating component being spaced apart from each other and connected with each other via a thermally conductive silicone rubber, the heating component comprising a core tube and a positive temperature coefficient thermistor disposed in the core tube wherein the heating component preferably further comprises an insulating member disposed between the core tube and the positive temperature coefficient thermistor, and the insulating member comprises a ceramic plate, preferably further comprising a protective tube disposed on at least one side of the heating core, and a sealing-waterproof glue layer coated on the sealing-waterproof glue member,