A lock driving mechanism for use in a lock has an inner driving member having an inner panel, and an outer driving member attached to the inner panel and having an outer panel. The inner panel has an inner surface from which a lock core driver extends and connects to a lock core assembly of the lock and an outer surface on which an inner driver and an outer driver are formed. The outer panel has an inner surface on which an inner limiting protrusion and an outer limiting protrusion are formed, and an outer surface from which a latch driver extends to connect with a latch bolt of the lock. When a key inserted into the lock core assembly rotates, the inner and outer driver rotate, synchronously push the inner and outer bump, respectively, to make the key and latch driver rotate smoothly to drive the latch bolt to lock or unlock a door.