To provide a peeling solution for salvaging the inner surface of a cathode tube on the basis of the action of microorganism in no use of chemical and provide a method for peeling and removing the materials inside a cathode tube.

A microorganism-culturing solution is prepared by symbiotically culturing (a) a group of aerobic microorganisms, (b) a group of anaerobic microorganisms, (c) at least one kind of basidiomycete in Hitatake and (d) photosynthetic bacteria and the solution contains enzymes originating from these microorganisms and a carbon decomposing enzyme. The resultant solution is diluted with water and the dilute solution is brought into contact with the cathode tube including inner material to peel and remove the inner material in the cathode tube.