A water heater comprising: a heating part including a burner configured to cause a combustion reaction from air and a fuel, and configured to generate heating water by using heat generated through the combustion reaction; and a humidification part configured to generate steam by steaming water by using a combustion gas generated through the combustion reaction and discharged from the heating part , and to provide the steam, together with the air, to the burner, wherein an outlet of the humidification part , from which the air and the steam, which are to be provided to the burner , are discharged, is formed to face a lower side of the humidification part , and wherein the water heater further comprises: a burner air supply pipeline connecting the outlet of the humidification part and the burner ; and a siphon part connected to a lower side of the burner air supply pipeline at an inlet of the burner air supply pipeline on a downstream side of the outlet of the humidification part with respect to a flow direction of the air and the steam , while having a "U"-shaped part such that the water, which is collected, is discharged due to a siphon phenomenon when a volume of the collected water becomes a specific volume or more while the water that flows down from the burner air supply pipeline is collected to define a trap. a heating part including a burner configured to cause a combustion reaction from air and a fuel, and configured to generate heating water by using heat generated through the combustion reaction; and a humidification part configured to generate steam by steaming water by using a combustion gas generated through the combustion reaction and discharged from the heating part , and to provide the steam, together with the air, to the burner, wherein an outlet of the humidification part , from which the air and the steam, which are to be provided to the burner , are discharged, is formed to face a lower side of the humidification part , and wherein the water heater further comprises: a burner air supply pipeline connecting the outlet of the humidification part and the burner ; and a siphon part connected to a lower side of the burner air supply pipeline at an inlet of the burner air supply pipeline on a downstream side of the outlet of the humidification part with respect to a flow direction of the air and the steam , while having a "U"-shaped part such that the water, which is collected, is discharged due to a siphon phenomenon when a volume of the collected water becomes a specific volume or more while the water that flows down from the burner air supply pipeline is collected to define a trap. a burner air supply pipeline connecting the outlet of the humidification part and the burner ; and a siphon part connected to a lower side of the burner air supply pipeline at an inlet of the burner air supply pipeline on a downstream side of the outlet of the humidification part with respect to a flow direction of the air and the steam , while having a "U"-shaped part such that the water, which is collected, is discharged due to a siphon phenomenon when a volume of the collected water becomes a specific volume or more while the water that flows down from the burner air supply pipeline is collected to define a trap. <EOS>