A water filler includes a water filling device, and a regulating device. The water filling device includes an inner filling tube, an outer filling tube, and an upper cover. The regulating device includes a floating barrel, a sliding barrel, a water support disk, and an adjusting unit. Thus, the floating barrel is lifted instantaneously and rapidly to stop the water filling action exactly and actually, thereby saving the water source. Thus, the water filler has a quick water stop function.