A liquid vaporizing and feeding apparatus, having high heat transfer efficiency and capable of producing a large flow of vaporized gas from a small amount of liquid, utilizes an inclined vaporization plate which is held at a set temperature by a heater. Liquid, discharged by a nozzle in the vicinity of the upper end of the vaporization plate, is vaporized as it flows down an inclined upper face of the vaporization plate. When the volume of the liquid collected on the vaporization plate 20 reaches a designated amount, a level sensor 40 stops the inflow of liquid through the nozzle. Then, as vaporization continues, and the liquid level falls, the sensor causes inflow of liquid to resume. The cycle of stopping and resuming flow of liquid is repeated to maintain a constant liquid level.