A cooking appliance is provided. The lid comprises a pressure-limiting valve, a lever, and a button assembly comprising a steam-discharging button and a button seat, the steam-discharging button being fastened to the button seat and being vertically movable for actuating the lever to activate the pressure-limiting valve for steam discharging. The button assembly comprises a guiding rod, the steam-discharging button comprises a heart-shaped groove. A downward movement of the steam-discharging button causes a first end of the guiding rod to slide within the heart-shaped groove. When the steam-discharging button is released, the first end of the guiding rod slides to a position for lockingly engaging with the heart-shaped groove, to keep the steam-discharging button at a steam-discharging position. Pressing the steam-discharging button once will lock the steam-discharging button for continuous steam discharging without the need to keep holding the button, thereby simplifying the discharging operation over prior art.