To provide a method for mounting a lithographic printing plate by which a flexible printing plate can be mounted with a high position registering accuracy in a simple method without interposing a specially processed block copy sheet.

This method is intended for mounting on the plate cylinder of a printer a lithographic printing plate for which a material other than a metal sheet is used as a substrate, and is characterized in that silicone oil or silicone grease is previously applied on the plate cylinder or the block copy film stuck on the plate cylinder for adjustment of the thickness.