A method of controlling steam supply in a laundry machine. The control method includes heating a predetermined space within a duct in communication with a tub and/or drum of the laundry machine to a higher temperature than a temperature of the other space within the duct, directly supplying water to the heated predetermined space to generate steam, supplying air flow towards the heated predetermined space so as to transport the generated steam to the laundry, and adjusting an implementation time of the heating based on actual voltage of power supplied to the laundry machine.