PURPOSE: To provide a method of mending a ceiling finishing member in a sprinkler facility, which can readily carry out a mending work around a sprinkler in such a case that a large size aperture which cannot be covered with a decorative cover is accidentally formed when a sprinkler head attaching hole is formed.

CONSTITUTION: A mending piece 8 having a shape corresponding to that of a part 7 to be mended is cut off from a material the same as that of a ceiling finishing member, and an auxiliary cover 9 is attached to a sprinkler pipe 3 on the back side of the ceiling so as to be slidable and securable. After the mending member 8 is bonded to the lower surface of the auxiliary cover 9, a slot formed in an aperture is filled with putty for surface treatment.