PURPOSE: To provide an operation control method for an automatic water feed device by which stable feed water can be obtained.

CONSTITUTION: A pressure tank 8 and a pressure detecting means 7 are connected to the delivery side of a pump 1, and operation and stoppage of the pump 1 are controlled by means of a signal from this pressure detecting means 7. A feed water quantity in a feed water condition is found from a signal value variation by carrying out an arithmetic operation, and operation and stoppage points of the pump 1 are selected from plural number of points according to the feed water quantity. Pump operating times are also similarly selected from plural number of points according to the arithmetic operation feed water quantity. Thereby, since a control pressure value is set successively according to the feed water quantity, stable feed water hardly causing a pressure variation can be obtained still in such a low cost simple constitution as an automatic water feed device.