To secure a stable water quantity and pressure when operation is conducted while a plurality of pumps having different displacement are changed over, and establish such a condition as is free of the pump shutoff state so as to assure a safe operation.

A water delivery control device 1 according to this invention includes a pressure regulation part 13 to calculate the value of a pressure command 10, a motor operation command part 14 to calculate the control commands given to motor control devices 4 and 5 of a plurality of water delivery pumps 6 and 7 on the basis of the result of the pressure regulation part, and a pump changeover judging part 11 to judge if changing-over to a different displacement pump is necessary according to a change in the water delivery quantity, and is structured to conduct a pump changeover control by controlling the number of revolutions according to the change in the water delivery quantity while a plurality of pumps are put in parallel operation, wherein the arrangement further includes a speed calculation part 12 which controls at changing-over of pumps, the number of revolutions of a second pump so that the discharge pressure at starting of the second pump 7 to be started subsequently becomes smaller than the discharge pressure of the first pump 6 to be started preceedingly.