An automatic fluid pump includes a pump body having a liquid channel and a mounting channel, the liquid channel having an inlet and an outlet and connected to a suction pipe and a delivery hose, respectively. A motor fan is disposed at a lower end of the suction pipe. A power controller is coupled to the pump body and circuit-connected to a battery, a terminal plate, and a switch. A valve case is coupled to the mounting channel in the form of a hopper formed at a lower end thereof with an inclined portion having an air hole. A valve case cap is coupled to the valve case. A main check valve is disposed on a lower surface of the valve case cap to open/close the through-holes. An auxiliary check valve is vertically moved up and down between the mounting channel and the air hole to open/close the air hole.