A restarting device of a pump including a center rod defining fluid delivering chambers and driving chambers 11b and 12b. The restarting device of the pump further includes: a change-over valve 2 for switching a direction for the center rod to move, and a restarting hydraulic circuit 3 which, when a supply of the driving fluid from the change-over valve 2 to the driving chambers 11b and 12b in both sides is stopped, detects the supply of the driving fluid into the driving chambers 11b and 12b in both sides having been stopped and then causes the driving fluid to flow into the change-over valve, thereby restarting the supply of the driving fluid into the driving chambers 11b and 12b.