To constitute a photographic printing system which ensures easy cleaning of a developing and transport path of a photosensitive material.

A transport roller R pair of a relay transport unit for feeding printing paper P to a developing and transport mechanism C of a developing section from an exposure section is freely openably and closably constituted, and an opening and closing door section 10Z is disposed in an area near the transport roller R pair of the relay transport unit included in the casing 10 of a printing block. A controller for controlling the exposure section and the development section executes the processing in a cleaning mode for driving the developing and transport mechanism C in the state of stopping processing in the exposure section. In the cleaning mode, the cleaning in the form of feeding a cleaning sheet S to the developing and transport mechanism C by opening the opening and closing door section 10Z and opening the transport roller R pair is realized.