PURPOSE: To facilitate the operation for replenishing and/or replacing the liquid by a method wherein a container provided with a small hole in its side wall or bottom surface and having a sealing stopper detachably plugged into the small hole is connected to the bottom part of a liquid-collecting pan through a flexible tube.

CONSTITUTION: The flexible tube 14 is connected to the bottom part of the pan 11 used for reserving the washing or damping liquid in a printing press or the like, and the upper-end opening part 15a of the container 15 for the supply and replacement of the liquid is attached to the other end of the tube 14. The small hole 17 is bored in the lower part of the side wall of the container 15, and the sealing stopper 19 is fitted into the small hole 17. In the case of supplying the liquid into the pan 11, the container 15 containing a predetermined required amount of liquid is connected to the pan 11 through the tube 14, then the container 15 is inverted and held at a predetermined height. Then the stopper 19 is removed so as to feed the liquid into the pan 11. In the case of draining the liquid from the pan 11, the container 15 is held in its normal upright position at a place below the pan 11.