PURPOSE: To prevent photosensitive paper from being contaminated by water drops by inclining the surface of an opening of a V-shaped tray for supplying a developing solution, fitting a sheilding member having a water drop preventing sheet over the surface of the opening and heating and evapolating the developing solution.

CONSTITUTION: An opening 1a of a V-shaped tray 1 is mounted so as to be inclined and developing solution 3 (ammonia water) is supplied from a feeding pipe 2 to the tray 1. A guiding member 6 using plural wires is fitted to the opening 1a and a shielding member 7 is arranged over the guiding member 6 in parallel. Plural water drop preventing sheets 9 are fitted to the shielding member 7 and brought to contact with the guiding member 6. When the ammonia water 3 is heated by a heater 4, evapolated gaseous NH3 and H2O rise up to the opening 1a, the space between the guide member 6 and the shilding member 7 is filled with these gases and the gaseous NH3 is not leaked. Water drops 10 adhered to the shielding member 7 are collected into a water drop sink W of the water drop preventing sheet 9(ii) and removed to the external. Photosensitive paper 8 carried from the arrow A is prevented from being contaminated by water drops.