A plate replacing apparatus for a printing press having plate lockup devices for fixing the two ends of a plate located in a gap of the circumferential surface of a plate cylinder and wound around the circumferential surface includes an old plate holding mechanism and a new plate holding mechanism. The old plate holding mechanism receives and holds an old plate removed upon release of the plate lockup devices and pivotal movement of the plate cylinder. The new plate holding mechanism removes the old plate and feeds a new plate to the plate cylinder.