To provide a cooling water circulating device, wherein the cooling water in a tank can be easily changed.

A work is moved and positioned on a worktable in a work transferring direction, and is thermal cut by a processing head freely movable in the direction orthogonally crossing the work transferring direction at right angles. The worktable has a slit hole 45 at the bottom position of a path in which the processing head moves, and a water path 47 having a spraying pipe 49 below the path. At the time of thermal cutting, the spatter dropping to the water path 41 is washed by water. A water tank 53 is installed below a drain outlet 51 of the water path 47, and the water in the water tank 53 is pumped up by a circulating pump 55 and again supplied to the spraying pipe 49 via a flexible supply tube 59. The supply tube 59 is detachable to the spraying pipe 49 by a connecting tool 63, and so the connecting tool side of the supply tube 59 is easily connected to a waste container. The circulating pump 55 performs the functions as a cooling water circulating pump and a water changing pump, and cleaning of the water tank becomes easy, resulting in shortening the time.