The present disclosure provides a cap and a water-heating device having the same. The cap for covering a top side of a case of the water-heating device includes a cover having a receiving space that is open at the bottom, the cover including an exhaust hole formed therein for releasing exhaust gas in the case to the outside, and an exhaust duct that is received in the receiving space and coupled to the cover and that forms an exhaust channel that connects an exhaust tube included in the case and the exhaust hole and releases the exhaust gas, in which the exhaust duct is formed of a material different from a material of the cover, and the material of the exhaust duct has higher heat resistance than the material of the cover.