A heating device capable of heating a processing liquid stably and efficiently is provided. The heating device comprises a first unit heater including a first flow path, a second unit heater including a second flow path, and a first tube connecting the first unit heater and the second unit heater, wherein a processing liquid flows through the first flow path, the first tube, and the second flow path, and is heated by the first unit heater and the second unit heater, wherein the first unit heater comprises a first pipe extending along a first direction and including the first flow path formed therein along the first direction, a first input terminal formed on a surface of the first pipe and extending in the first direction, a first output terminal formed on a surface of the first pipe, extending in the first direction, and spaced apart from the first input terminal, a plurality of first heating wires spaced apart from each other, formed on a surface of the first pipe, and connecting the first input terminal and the first output terminal.