To provide an energy-saving lifting pump device and its operating method, for securing an optimum pump operational status, in contradictory pump specifications of high lift and low lift before and after providing siphonage.

A plurality of lifting pumps Pa, Pb are connected in series with each other, a suction port 3a of the lifting pump Pa of the start end part is opened to the inside of a suction tank 1. A discharge pipe 4 led upward from the discharge port 3b of the lifting pump Pb of the ultimate end part has a tip opening part 4e led down below the water surface of a discharge tank 2. All of the plurality of the lift pumps Pa, Pb are driven in starting the lift. When the siphonage is provided between the suction tank 1 and the discharge tank 2 through the discharge pipe 4, only the minimum numbers of the lifting pumps are operated and the other pumps are stopped to function as a discharge water passage or a suction water passage.