To restrain the staining caused by preheating immediately after replacement of a mold bladder for tire vulcanization without the use of a stainproof ring.

This mold cleaning method comprises the processes for: first, opening the mold and removing a used bladder to fit a new bladder (process S1); closing the mold, then storing the mold in a vulcanization machine not illustrated; preheating the bladder after preheating the vulcanization machine (process S2); and again, opening the mold and cleaning the upper surface of the lower side mold and the lower surface of the upper side mold with the help of a cleaning robot (step S3). Thus, it is possible to restrain the staining caused by the preheating immediately after the replacement of the mold bladder without using the stainproof ring.